There aren't many benefits, I'm committed to my partner and we've been together for 7 years now. She's my life partner. Getting married doesn't offer much that you can't already do with other legal documents, such as getting the same rights to them in medical situations as you do with marriage. Tax benefits maybe
Neither of us want to get married because it does nothing for us, were already each others partners, even if we did, after marriage I would still refer to her as my life partner instead of wife.
Plus her very religious family desperately want us to marry and we both want to keep denying them that pleasure as early on in our relationship they were adamant we would split up if we didn't get married before living together.
Most people are unintelligent sacks of meat, not much critical thought about what they do runs through their minds.