After a 22 year trial period, we married for insurance purposes.
However, my current partner has better retirement benefits than I do (both Social Security and pension benefits). I recently joked with him that we should marry so that I inherit his benefits should he kick off before I do. That would be an unpleasant reason to get married.
Regarding health insurance, currently it looks like we're better off not being married. That's probably also true for tax purposes.