I can't answer for the east coast, but I can shed some light on Arizona, Nevada, and Ohio.
One of the trends has been towards the rock-n-/extreme/glow/whatever-bowling, especially on Friday and Saturday nights. Even from a capital expense point of view, proprietors seem to be spending more money on music sound systems, black lights, and flourescent furniture and appointments than spending money on more traditional items such as the commonly half-broken lane-conditioning machine. Take a look at where the money is being spent and that is usually a good indication of what the proprietors believe to be the big money source.
Another (disturbing to me) trend has been the "bowling birthday party". I've had several managers tell me they'd rather fill the house with birthday parties than leagues because they make more money per birthday party. The reservations for these things get scary on the weekends. To share a personal experience, I walked into a 32-lane house at 10am on a Saturday not long ago. There were a total of 3 lanes (not pairs) in use at the time. When I asked for a lane, the desk clerk asked me if I had a reservation. Since I didn't, he could not give me a lane. They were "booked" with birthday parties starting at about 11am, and he didn't want to give me a lane for fear of upsetting the incoming birthday parties. $40 bucks gets you an hour of lane time, some party favors, a small cake, soft drinks and some hot dogs for the kiddies. Some places even give you an autographed bowling pin. The $8-9 dollars they were going to get from me for the hour just wasn't worth it, so I was turned away.
Second-shift leagues are on the decline when you can find them at all. They seem to be unheard of on Friday and Saturday nights (rock-n-glow-extreme bowling). However, many of the houses are filled with leagues on the first shift Monday through Thursday. Surprisingly, the non-smoking leagues seem to do especially well.
I've heard several exasperated bowling center managers explain that league bowlers do nothing but complain about lane conditions and prices. Lineage did not increase one penny in any of my three leagues over the last two years, but I've seen birthday party prices increase 4-8 bucks. Perhaps if league bowlers in general were willing to spend a bit more in lineage and do a little less complaining about league fees, center managers would be happier to have them.
Don't construe any of this as anti-league. I've been a league bowler for more than 25 years. These are just observations and conjecture.
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Kill the back row (or maybe this should read "make your spares, dummy")