Joe, here's my take for whatever minimal value it might have:
I think you've hit on one of the major hurdles to all performing musicians these days. Used to be, you could learn a set of songs that could be played to any audience, but those days are long gone. As I see it, here are today's options:
1) become a DJ. I think the main reason DJs took over the wedding market is because the demographic at weddings is so varied that it would be hard to know enough songs to please everybody. A DJ can easily get a song list from clients and come prepared to play exactly what they want. If you want to perform, start by sprinkling a few performances in with the DJ songs to see how they go over.
Hi Pat. The DJ thing might be what happened in your area but not here. The real reason that DJs took off here was cost. DJs undercut bands by at least half. A good wedding band would cost $500 USD or more. DJs came in at $250. That ended most all of the wedding bands in this area.
Also a good wedding band should be able to cover all age groups. My wedding band had a repertoire of 350 songs, plus fake books and we could jam with no problems. We had no problems satisfying wedding crowds. Plus we were not unique as many wedding bands around here were the same as ours.