For some reason they assume they ought to be good from the beginning. Even in their first game they try to be original. They're afraid to imitate moves they saw someone else play. It feels like watching someone trying to learn a language by not imitating the sounds they hear when others speak it.
But those that i saw who became really good, were always on the other end of the spectrum. Those who jump right in and played /really/ bad without any anxiety or pressure (no thinking at all and mostly just stubborn imitation of moves they saw someone else play before) and fast (many many many games, often not even to the end), almost always sticked to the game long enough to learn to appreciate and enjoy it, and sometimes even managed to excel at it.
There's something magical about the fearlessness of just playing. Pure curiosity, maybe even quite a bit of ambition, but especially the absolute surrender to repeated and premeditated failure.