I simply can't stand not knowing something.
For example, I might hear two people on a train trying to remember the name of a hotel that they stayed in twenty years ago and mentioning things like the town it was in, that it was rather posh (with a commissionaire on the door) and that it had a French restaurant. When I get home I just have to spend time researching an answer to their question, even though I'm never going to see them again in order to be able to give it to them.
I can sometimes research dozens of such answers in a single day. If I remember such a conversation at 4am, I have to get out of bed to attempt find to find an answer to it, as I won't be able to sleep until I do. There have even been times when I've suddenly recalled such a query many years afterwards; I still have to attempt to find an answer to it.
So if I get stuck on a crossword clue, it's very important to me that I find out what the answer should have been, otherwise I won't get any sleep that night (and possibly for many nights after that, perhaps even stretching into several years too)!
I never submit entries to prize crosswords and I never google for answers to clues that I'm personally stuck on until I've simply given up hope of ever getting the answer right. (I do, however, frequently google for help in answering crossword questions posted by others here on AB).
So I can well understand others who 'just need to know the answer'!