The old time greats leaned pool through their pockets, the path was to gamble and play against better players, loose a lot until you can win.
This might have worked in gamblers scenes, and tournaments back then were no more than hustlers conventions... this attitude can not beat a well trained athlete. A street fighter won't beet a top pro boxer in a pro boxing match.
The gambler mentality still rules America pool.
It's not as if there are no gambling in other countries, sure there is and most of the top players gamble or play money games, but the learning path is different.