I don't force myself to (for instance I have a DS and probably would not enjoy enjoying having 'only' a GBA, although I enjoy some GBA games on the DS) but I also like to be on the trailing edge.
There are numerous benefits:
- you don't beta-test the game, i.e. you get patches that solve most of the issues
- you can get user/fan generated content: new patches (for Master of Orion 2 for instance), maps/mods/gametypes (UT2004)
- FAQs are available and quite advanced so no need to try and spend 5 days trying to guess how to get that ultimate weapon or whatever.
As for online playing, I can say that at least for UT2004, those who remain are among the 'best' (friendly, with good knowledge of the game) players (roughly 40 to 50% of the best 'moved' to other games, so that's 50-60% that remain).