I don’t think anyone can say for sure, there are only theories. I would say that 9 ball is a better gambling game which probably hastened the transition. It’s also a quicker game to play. And also, amateurs tend to follow the lead of professionals. So as the pro tours transitioned to 9 ball I’d say more and more new players did as well.Anyone know what turned 14.1 from the most prominent game played on a table with pockets to the niche it is today? And what made 8 ball take over as pretty much the only game casual pool players have ever tried (other than 3 ball)?
As far as 8 ball, I think there are likely two factors. In the last 30 years I would guess most people’s introduction to pool has been on a bar box. It was for me, and going based my experience talking to casual players, they all see pool as synonymous with a bar activity. 8 ball is the perfect game for a coin op table, since it takes players long enough to get through it to get their money’s worth. It’s also perfect for beginners. They have 7 shots to choose from and even a beginner can run 6 balls occasionally. I’ve seen casual players try 9 ball, but generally they retreat back to 8 ball after a game or two. For most of them 8 ball IS pool.
I think pool is a bit of an oddity in that we have some very avid players that never progress past casual play. So you get generations of players who never played anything but 8 ball and teach others that 8 ball is the game of pool.