Close.. What it basically comes down to is this:
Young males, once they hit puberty, beccome intensely competitive. We are mammals, and like all mammals, once we hit a certain age, we have an intense biological urge to "stake our claim" and gain territory. The way this is done with other mammals is by males all competing against each other, in.. Whatever.
Almost every sport/competitive hobby relies on this natural competitive urge. Young males begin competing as early as the particular game/sport allows them to.
Now... Because of rising rents, pool halls are expensive to run. So alcohol is almost a requirement. Which means young, aggressive, competitive males cannot compete in them until 21. MUCH too late to grow a competitive group.
These young, aggressive, competitive males are going to be biologically driven to compete at SOMETHING between the onset of puberty and 21... And so they are going to compete at the thing they can compete at with relatively small investment and constant availability - video games. And it doesn't hurt that the video games are tuned to hit all the pleasure centers of the brain in the strongest way, without actually ingesting drugs.
So, there you have it.. Yes, kids are playing video games, but their loss of interest in other hobbies is in part because those hobbies (specifically pool) do not make themselves available to the youth, and so, pool loses out on capturing these kids during the onset of their strong competitive urges.
By the time a kid reaches 21, they've been playing video games for quite a few years, and might have even burnt out the competitive urges by that time.
So... Get kids playing pool around 12, or the game dies when the current crop of 40 year olds gets too old to play.