The insurance should not be an issue, as the partner can be named as beneficiary on any life insurance. Where this would come into play, would be to allow the “spouse” to automatically inherit all or some of the assets. Without the “spouse”, those assets would likely be split (depending on Ohio law) between parents, children, or siblings of the decedent, assuming no valid will is in place. So this would allow the spouse to trump other blood relatives for part or all of the assets at death.
A will would do the same, so I don’t see that as an issue. Nobody is entitled to the money of another at death.
It would allow a gay spouse to get the benefit of any marriage adjustments in the estate taxes — spouses can inherit with no tax in most cases. But I can’t say I’m all that upset about that, because all of us should be able to inherit without tax (and most of us will, at least federally, with the 5 million deduction).
That is why they chose this case — it is the one most likely to invoke some level of sympathy even among opponents of SSM. Once this case grants the right, then they get it all, like forcing christian business to provide spouse benefits for same sex couples.