As a USBC director and Association office staff, I can say that our number of bowlers have not dropped in the last year or so. But they have declined over the last 6 to 10 years. This is probably typical for all the reasons already given. But our winter season is really really busy. It probably has a lot to do with being in CA where the weather and road conditions are always good. So seniors, especially, can get to the centers. Over 50% of our sanctioned bowlers are over 55. I saw this problem when I visited my Dad in Indiana. In winter a lot of seniors don't want to commit due to weather and road issues (in other words transportation) and in summer a lot of them leave for warmer locations. Short of going to their homes and bringing them to the bowl in bad weather , I don't know how to fight that.
But a couple things have helped some of our proprietors. 9 pin no tap leagues. Yes you can sanction them and yes they can get awards, just not average based awards. But a lot of seniors don't see the need to sanction, so we also have a lot of non sanctioned senior leagues, regular and no tap. That hurts the local association numbers, but not the proprietor so it might be an idea for you. We also have "learn to bowl" leagues that are fairly short in duration, and the prize fund goes into a new reactive ball at the end. Coaches are on hand and there's a clinic atmosphere for the first three weeks or so. The league I believe runs 12 weeks. Again, this is not a sanctioned league in this case. We've seen an increase in 1/2 season leagues. So the 34 week commitment is down to like 14 or 16 weeks. You are probably already doing this, but free coffee for morning and day leagues. I don't know why, but free coffee can make the difference between seniors bowling at one center vs the other. Our center feeds them a light lunch every other week too; I think they are charged like a dollar or something in a can on the honor system. Its just simple sandwiches and chips but its all gone by the end of the bowling. And of course the day lineage fees are much less then night. One center charges only $3 lineage, the whole league dues are only $6 per person per week. That league has over 125 senior men (only) in it.
Night leagues again seem to all boil down to lineage costs. Houses that charge less are typically full. The local AMF houses, that always seem to charge more then the privately owned centers, are not full at night. Monday night became an issue in our center. No TVs on the concourse and leagues were going to leave because they could not watch Monday football. Solution.....TVs were installed. Not fancy flat screens, but TVs none the less.