There's a difference between being equal and being identical. One of my boyfriends and his wife have an astonishing number of children, mostly under the age of 12. Obviously, he needs to spend considerable time ensuring that they are healthy, well-fed and happy.
I have two cats. I don't need him to spend any time making sure of their health and happiness, so I don't need him to be around as often or for as long as his wife does. If I was one to insist on capital-E Equality this would be untenable, even though what his wife is getting is not something I actually need or want.
You may have seen this image floating around on the internet recently, which I think sums it up nicely:
I don't insist that it's my right to have a box to stand on just because my metamour needs one.