Creampuff, too many people take advantage of the fact that something isn't "Compulsory", sticking to the bare minimum gives you the bare minimum of safety as well.
Gliders and Ultralights, they might not necessarily REQUIRE one but for $200 or so you can buy yourself a handheld VHF and at least listen in, buy a map for a few quid as well so you know what to listen in on. Just because you don't HAVE TO, doesn't mean it isn't a bloody good idea. Problem is it seems to require that little bit of extra effort people can't be bothered putting in.
If you're in something larger then you really should have a VHF radio installed, 2 preferably or one that allows you to monitor a standby frequency as well, it's not difficult, it is a little expensive, but personally if it can save my life and possibly the lives of those around me I'll probably forego a few nights out and set aside a little extra for some extra equipment.
Of course there are limits to this argument, obviously we're not all going to be able to afford to install a couple of top notch GPS, Weather Radar, EGPWS, TAWS etc...etc... but just a few simple items like a handhelp GPS and a VHF radio shouldn't be too far out of reach for most people.