I’m 36 and have been with my current girlfriend for almost 5 years now - my longest relationship yet. We live together & everything else couply, just not married. I see marriage as unnecessary pressure that has a tendency to put strain on the relationship. Right now if we’re happy together we stay, if we’re not we split. Simple. Marriage complicates it.
We got married for legal reasons. It’s much easier to get married than to get power of attorney, wills, and all that legal stuff done separately, so one day while sitting on the sofa looking at that stuff, I just said “hmm, you know, getting married is much easier”. And that was our proposal.
We got married with just our close relatives there, because my mom would kill me if I didn’t invite her, and his grandma would help out.
We DID have a big 10 year anniversary, because we wanted an excuse for a party, but it wasn’t wedding-like at all.
In addition to that, having kids, crossing international borders and moving to different countries are also things where marriage gives benefits.
And in some jurisdictions, there can be very significant tax advantages.
Which is why there was always a big fight for marriage equality.
But if you don’t want all these legal benefits, then co-habiting is fine.