I've been playing Minecraft on my iPad pro (m1 chip) these days. In v1.17.30 and in a world that I've been playing survival mode all the time, I found that all creatures, including animals and villagers, disappeared when I came back from a place 100 blocks away, even if I fenced all of them and ensured that there's no way out. Name tags and trading doesn't help preserving the villagers. In fact, there has been some missing villagers and animals every time I entered Nether and came back (or went to a far place and came back), but not all. It's really weird that this time, all villagers suddenly disappeared, and I was literally staying in the main world around them.