Is it not also an attitude thing?
I.e. gliding is (and is perceived to be) a sport - and for a sport, you wear proper equipment.
SEP flying is not seen as a sport but as a way (crazy as it sounds) of getting somewhere (even if it is a bimble), so you wear the same as you would if you were driving a car.
Cue the usual discussion regarding whether or not we should wear gloves, Nomex suits or the like...
Has any actual research/test been carried out w.r.t. exiting a spamcan? Apart from exiting, what about the empannage (or wing strut, indeed)? Are there any stats on 'injury/death could have been avoided by bailing'?
As an aside, without a functioning autopilot and controllable plane, between the pilot letting go of the controls and exiting the plane, the attitude is un likely to be conducive for a safe exit?
There are some stats
quoted by an AVWeb article on ditching - and they look substantially better than 50/50...
Baikonour