I have two road bikes, one is a triple and one single, so I don't have an informed opinion about maintenance on a double. But I have no particular reason for the triple; it's what came on the bike and is just extra weight as far as I'm concerned. The best approach is to look at the terrain you'll be riding, figure out the minimum gear inches you'll be happy with, then compare that to the charts of various configurations. Then keep in mind that the advantage of the smaller ranges in cassettes are the closer spacing of gear ratios between shifts.
The very top gear - 52x11, 48x13 or whatever - is more a "specialty" gear than anything else. If you want to push your speed downhill, have the best possible sprint, keep up in the draft of a really fast rider. So to answer your question about the trend and 20 speed bikes, there's a good reason for all of the configurations. Personally I'm a bit of an iconoclast that I'd rather have an 8 speed cassette, for the better durability and cheaper maintenance. I have a 1x8 on my commuter road bike, perfect for my commute but more challenging on our hills.