I'm not sure whether, statistically, scuba DOES have a higher death rate than other "risk sports" or not, but I think a contributing factor to deaths in diving is the percieved ease of diving..... Many other sports have a way more self limiting factor preventing people who aren't ready for it getting in too far over their heads - for example, mountain or rock climbing - extremely unfit people, or those with insufficient skill are unlikely to be capable of putting themselves into high risk situations - if you can't make it up the cliff in the first place, you can't fall off it!
With diving on the other hand, it is relatively easy to get in WAY out of your depth (pardon the pun), with the need for all that extra training and a basic level of fitness only becoming apparent to the unwary when it starts hitting the fan - by which point it is of course too late for such insights.
In some other sports (climbing, paragliding come to mind) you need a certain level of ability and expertise in order to physically put yourself in high risk situations. In scuba, getting into these situations is often fairly easy - its knowing not to go in the first place, or getting out of them once there that requires the skill!
Edit: I just thought downhill skiing may be similar.... when you get off the chairlift, and think "oh C**P". Although, for your average recreational skiier, making such a mistake is most likely to result in an undignified descent, possibly a ride on the ski patrol's "snowmobile of shame".....the stakes are kind of higher in scuba.
