Your answer to the above might be "never". Which is totally cool.
But I think lots of people like rewatching favourite content, and YouTube is no different in this regard.
They don't care about recommending you something new, they care about recommending you something that you would watch.
I honestly don't very often, and when I do it tends to be over a span of time long enough to forget many of the details. I do have some music videos on youtube that I have watched several times, and some instructional videos I have returned to occasionally.
So yeah probably its the weakest of my three whines.
Very rarely. Even more rarely do I re-watch movies less than a month later, but that doesn't stop Youtube from recommending things I watched the day prior.
If I got recommended something I watched a year ago, sure. But what youtube frequently does is just recommend all of the videos I watched the day prior.
I would be less annoyed if this wasn't such a recent development. Youtube recommendations used to be fantastic for me ~5 years ago. I would actually get recommended stuff I haven't watched, from creators I didn't know about, on topics that I have shown interest in. Now I mostly just get the same videos I have already watched or nearly the same video uploaded by another channel. Or I'll watch a single 15 second video about something I normally don't watch, and suddenly half of my recommendations are about that.