A good reason: If it's culturally expected and universal in the country you live in.
Or even in expected in another country, e.g. I almost married my Turkish girlfriend a few years ago. (The relationship ended before that happened, very long story) I'm in Australia, but that really felt like we were in Turkey. Couldn't walk down the street holding hands, because Turkish people would see and the family would find out. It seemed having a boyfriend is a kind of shameful, bad thing for a woman, but suddenly if you get married, it's all wonderful, you're no longer fair game for harrassment etc. I've never wanted to get married in the least (it never came up with any girlfriend I'd had before that), and don't know how anyone can promise to love another forever - but to make my partner and her daughter's lives better, in many ways, so easily, seemed a very good reason.
> ... to make my partner and her daughter's lives better, in many ways, so easily, seemed a very good reason.
By obeying the "boyfriend is a kind of shameful, bad thing for a woman" logic one becomes responsible of "perpetuating" this backward, hurtful culture.
Or even in expected in another country, e.g. I almost married my Turkish girlfriend a few years ago. (The relationship ended before that happened, very long story) I'm in Australia, but that really felt like we were in Turkey. Couldn't walk down the street holding hands, because Turkish people would see and the family would find out. It seemed having a boyfriend is a kind of shameful, bad thing for a woman, but suddenly if you get married, it's all wonderful, you're no longer fair game for harrassment etc. I've never wanted to get married in the least (it never came up with any girlfriend I'd had before that), and don't know how anyone can promise to love another forever - but to make my partner and her daughter's lives better, in many ways, so easily, seemed a very good reason.