This is why it is not assimilationist for gay/queer people to want to enshrine marriage rights in their country/region
Similarly, this is why polyamorous people are fighting for the right to have their relationships recognised by their states through marriage and/or similar agreements
Oh, and because on top of those aforementioned financial and medical protections, these laws also help you maintain connection to any kids you have and/or raise together!
I would go further and say, this is why we really should be looking to expand some of these rights so that marriage is NOT the only way they should be enshrined. (e.g. Why could I get married tonight to a guy I met this morning, and get him on my health insurance, but I cannot do the same for a sibling?)