Just a little note of intro...I'm new here. I was an avid bowler during high school (back in the late 80's to early 90's)...stopped when I got to college (just too busy) and haven't really picked it back up. I went from a competitive tournament bowler on the youth/junior level, to basically bowling maybe 5 or 6 times over the next 25 years (and I don't think I ever really stopped loving bowling).
I think the reason for bowling's decline is merely the change in parenting styles over the past several decades. When I was younger, most kids had one activity at a time and it wasn't usually year round. I had baseball a night or two per week, maybe Saturday morning. There was time left over during non-baseball season or even DURING baseball season for parents to do other things...maybe go out to a Tuesday night bowling league with his buddies.
Nowadays, a kid who plays baseball also plays Fall Ball. He might go to clinics in the winter. He'll play on his little league team in the spring as well as a travel team that extends into the summer. He might also have a camp later in the Summer. And a lot of kids will have another activity on top of that that gets squeezed in. If you have two or three kids, there is absolutely no time left to commit. You certainly can't carve out one block of time each and every week at the same time. Add to the fact that today, most households are either single parent (divorced) or dual income (I.e., no stay at home parent). So, both parents are scrambling every moment they aren't working just to keep life moving forward.
I think the one way to fix it is to market bowling for the whole family. I started bowling again because I have a few kids who started league bowling this year. I have a couple special needs children (large, blended family) who aren't really suited for the typical baseball, football, soccer, etc. types of sports and needed an activity, so we got them into bowling. But, I think bowling *could* regain popularity if it was marketed a little better.
But if you really want *adult* participation, you have to target the "Mom/Dad audience". Youth/adult leagues are great for that. Also, I remember in my youth, some of the larger houses would have an adult tournament going on at the same time as youth tournaments (or have them back to back...youth in the morning, adults right after). Those were the ones my Dad would bowl in, because he was already there.
I think the other barrier was already mentioned...there is an intimidation factor that seems to be present now as bowling has evolved. Even as an experienced bowler, I find myself swamped looking at bowling today. 25 years ago, if you were aspiring to up your game, you'd by a Hammer. EVERY SINGLE decent bowler had at least one hammer in their bags (I had a Black Hammer, Blue Hammer and Blue Pearl...my Dad had a Black, Red, Red Pearl and a Nail). Now, I come on this forum wondering what the first new ball I should buy is and there are 117 PAGES of bowling balls. 25 years ago, we new about top weight, side weight. Now, I need to learn RG, differential, mass bias, PAPs, PIPs and POOPs (okay, I made some of that up). I know you can walk into a pro shop and have someone give you something appropriate...but there was a feel 25 years ago that if you bought a Hammer, you were serious. Now, it's just not the same. So, there's a barrier...even I feel it and I shot 268 last week bowling for really just the second time this year.
I liken it to video games. When I was a kid, even though I spent hours per day playing, my dad could just sit down and play with me. Games were simple and it didn't take much to be able to have fun together. Now, my kids ask me to play with them and I join there game and I have a character with an "inventory" that has 36 pages containing 197 different weapons and ammo. There is so much going on on the screen that I feel like I can't even really play. There's an extreme "barrier to entry", if you will. As such, kids don't play video games with their dads anymore (really).
I'm not even going to get into scoring. The number of 300 games being shot nowadays (even with less participation)...I don't think it's good for the game. I live in Delaware, so Jim Johnson Jr was a legend in Delaware when I was bowling (he was still bowling local and hadn't really gone on the tour yet). He held the ABC record for career 300 games at 27. I saw him bowl a few in local tournaments to get into the low 30's. Now, there are lots of guys with over 100? A 900 series was a legend...now it's been done over two dozen times? I think the inflated scores goes a long way to further divide the newer player from the "elite", to the detriment of the game's appeal.