The short answer is our brain wont let us forget anything we remember. The long answers are the "phantom limbs" syndrome and playing style fixation. One consolation is that these two can be blamed on someone else. The first, on your parents for not starting you young; the second, on your coach for your bad style, or leaving you without one.
Let's look at the above three answers one at a time. Our brain, unlike (and probably, thus, inferior to) the computer, does not have the ability to delete what's in it. So we are stuck with whatever, mostly bad, skills we learned. But to compound the bad situation, these problems are both physical and physiological in nature. We should go into them in details below.
The physiological problem is related to the medical phenomenon called the phantom limbs syndrome. This is when a person, after losing a limb, would still feel the existence of a phantom limb. The feeling is generally stronger if the limb is lost after teen age. But there are few, who were born without the limb, still grow up to feel there is something there.
Let's take a short and practical way to explain how this relates to ping pong. The comparison comes in the form of a rehabilitation process called "fusing". This is simply the adaptation of an artificial limb. Remember the basic premise is that the brain will never let us forget what we once had, or even what our parents had before we were born. To illustrate it explicitly, we will cite three examples.
A large majority of people without a limb would still feel sensations of pain and itch in it. Many who get old would suffer from arthritic pain in the joints of the limbs that do not exist. The problem literally becomes a nightmare when it occurs in the night, since you can not even soothe or scratch something that's not there. This is when fusing comes in. Even though it may take a long time to adapt to, or fuse with, an artificial limb, but once fused well, this actually could alleviate the problem of pain and itch. An often observed situation is that the nonexisting limb is always shrunk. Fusing can stretch it back to the normal length.
One example should be sufficient to make the point. But let's throw in two more to hit home on this topic. The first is a case where a little girl, born without arms, was able to count with her nonexisting fingers in doing arithmatics. And the second is about a navy admiral. After struggled but failed to lose the sensations in his amputated left arm for over half a century, he finally declared: "This proves the existence of a soul".
In a way learning ping pong is basically a process of fusing with the paddle. But this time we are fusing with an artificial extension to our hand. Just imaging if you lose a hand and the doctor put back an artificial hand with fingers that are two inches longer. The estranged feeling can turn into serious anxiety. This is the most common mental states of ping pong players exhibited on the table!
The preoccupation with not being able to fuse properly can distract a player from doing the right things, such as watching the ball and generate power from the waist. Ping pong is simple physics, but under stress, the body often works against what physics calls for.
So, what's the remedy? Just don't make the same mistake with your kids as your parents did with you. Start them young.
Well, if you do start young, you better also start right. This brings us to the next problem of style fixation. Children can learn naturally if we just give them the fundamentals. But often times, we also try to jam our own handups and wishfulness into their styles. And most of us, who learn ping pong as adults, basically pick up all our skills "from the street". This causes flaws in our styles that become permanent fixtures in our ping pong careers.
In a way style fixation can be compared to our lives' aspirations. We all strive to fit into slots that we call our stations in life. Ping pong is like a miniature rehearsal of life. We seem to all follow our individual, fixed paths. Normally, it's a near impossibility to change a player's fixed style.
To illustrate this explicitly, let make some common observations. Ping pong players spend most time strengthen their strengths, rather than fill their weaknesses. This locks them deeper into their defective style. It seems we rather spend the rest of our lives to gain another 100 ranking points, than sacrifice a few months to break out of this fixation, so we can remove the lid on our future improvements.
But to break out of this fixation is easier said than done. Basically this requires us to work on the weaknesses. The return is often uncertain, not to mention the skill level would sure to drop initially. The time span could be longer than expected, lasting from a few months to a few years. For upcoming elite juniors, this would mean a detrimental drop in ranking and a seemingly unrecoverable loss of opportunities.
In many cases, breaking loose from the style fixation requires letting go of some cherished skills. But these are exactly the skills responsible to bring a player up to and maintain him at his current high level. Here, the brain just simply wont let you forget.
In close, let's spend a few moments to turn our unsolvable problems into challenges. The phantom limb problem is being tested with the use of a unextended racket, dubbed inappropriately the "Cal Atomic" racket by a self-proclaimed marketing expert and a ping pong parent, Tong Lee. Alone with a fencing style of play, it, thus far, has only been demonstrated to be playable. We will be able to tell a little more in another year.
The solving of the style fixation problem has been tested on a top junior, Freddie Gabriel, with mixed results. Hopefully more parents and coaches can be convinced of the true existence of this problem and are willing to use thier players as guinea pigs to test it out. Thus far the only example of a successful demonstration is in the case of the tennis great, Pete Sampre. He changed from a two handed backhand to a one handed, struggling through all the negative consequences described above. But we still dont know whether it's the change that made him a champion, or it's the champion in him that allowed him to make the change.
As improbable as it is to solve these problems, their identifications give us a glimpse of hope. If American ping pong can not beat the the rest of world, maybe we can try to beat these identified problems first.