"Why should women have to pay for prostate cancer or testicular cancer?"  -- NOW you're getting it!  If all insurance markets were on an individual basis, and you only paid for things you wanted covered, it would single-handedly make costs plummet for everyone.
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"One big pool of risk" is not a "risk" at all.  It's just a lump sum of coverage, regardless of risk (That's the community rating fallacy imposed by Democrats).  Insurance companies simply say "Sounds great- everyone's premiums just went up 200% to cover for those at risk that we are forced to take."  And they do.  Until government once again kills industry and says, "hold on; on top of that, we're going to decide your charging limits and coverage minimums on top of that."  The market is killed and there is no incentive to even have insurance if it's that costly-- as evidenced by thousands of Americans more willing to pay the government gun-enforced penalty for not having insurance than actually having coverage. 
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