I have a mate whose partner asked her to marry him every time they had a major row. She reckoned he didn't really want to marry her or he'd ask when things were good. Or that he was looking for an easy fix to the situation. He never discussed or bought a ring.
He turned out to be a proper prat and it wasn't until many years and a bunch of kids later, they parted.
She said that quite early on in the piece, she decided she would not marry him at all and he probably knew it so it was safe for him to ask.
Later on it became a farce, she had said it straight out - and he would ask (with a smile) at the appropriate row time - she thought to annoy her.
Other friends did not understand it, but I think I can see her viewpoint. There were many things in their relationship that were red flags not to marry.
So why did she stay? She says she was not confident to start a new life alone. She was in an uncomfortable comfort zone. She was so busy with the kids - they were priority.
She says she's glad she didn't marry him. She went with what she felt and didn't get distracted with the romantic idea of a wedding that would have only postponed the ill feeling that was going on, that would have temporarily glossed over the problems and that would have made her feel trapped.