That is the case in many poly families, and I feel pretty much the same, however some people actually care about stuff like DNA and lineage. Having that as an option for some folks would be pretty cool. For instance, in cases where one person is infertile, they can still donate mitochondria.
I agree there are plenty of people who feel that way. I just question if healthcare providers will go along with it. Cases like this one where it's medically necessary are one thing, but "hey, Martha wants to be parent #3" is a different matter.
