Mark:
That certainly is something all of us ponder constantly and have done for a very long time.
How indeed, have sand bunkers become so much less penal than they once were and were originally probably intended to be, particularly in and with their lie and playable interior sand surfaces, while other hazard features such as water hazards, rough, trees etc, etc have become so much more penal over time?
My feeling is it all just evolved that way without much thought or forethought on the part of anyone but it's hard to deny the effect of it has been some kind of over-all "balancing out"----eg water hazards, rough, trees etc becoming more penal than perhaps they once were and sand bunkers so much less so than they once were.
Funny you mention that as I've just been conjuring up a comprehensive proposal (thread) on how architecture, maintenance and golf generally, including the Rules of Golf may be able to get away from this in the future.
I think you'll see that the way to do it can never be some "either/or" kind of thing. It needs to be considered in more of an "all-in" general and comprehensive kind of way, in my opinion.