The main reason is that the muscles of your palm become very strong and the palm will be very thick. The longer you practice, the thicker you will get. (But many hands are thinner and won't get thicker. It is impossible to exaggerate their bony hands. )

Also, even if you use the right hand shape, your hand will still tilt a little (this is because your fingers touch the keyboard, but most people's hands will tilt, not necessarily playing the piano)

The important thing is that you don't practice your hand shape when you have calluses.

Some people think that it will make their hands slim, and there is a certain chance. But if you practice from an early age, your hands will become shorter (or shorter) or even deformed. I belong to the latter category, and my little finger is thick in the second quarter.