One can argue about ELTs etc and anybody not carrying a raft when away from gliding range of land is a fool.
Wearing just life jackets, unless they are gliding in from FL200 in a motor glider (and thus give the rescue services a good head start), or they ditch close to some boat, they will likely be dead by the time the official helicopter reaches the scene.
It's a £1000 or so, but arguably this is the cost of expanding one's ability to go places in a plane.