right? I mean even the traditional marriage vows (which given the possibility of divorce aren't really to be taken literally) include the phrase "until death do us part", implying that you are free to find somebody else once your partner has died.

I think remaining unmarried after a death is mostly a function of the amount of effort it takes to build that connection again. For some it may seem preferable to keep true to a memory.

Oh, absolutely. I've never been married, but after my SO died, it was over a decade before I started dating again because I absolutely hate that part of starting a relationship.