I think you're right - it is more of a security blanket rather than a fix to a major problem. One reason why I would like it is for flight in IMC, but as Stik said, it's a rather large sky. When you get up on top, you hardly see anyone; what are the chances of bumping into someone in IMC on those occasions when a radar service isn't available?
I prefer to get a radar service and it does make me feel nervous when the answer to the question 'What stops us from hitting someone else?' is 'Luck', but that's the same stuff that stops most nasty things happening.
I suspect that that more lives would be saved if money was spent on more training rather than on more gizmos.