In my old world (made in 1.14) wandering traders don't spawn. I have been in the overworld playing, for many hours in multiple places (old chunks and new chunks) on the surface and no wandering trader is yet to spawn. When I have played on new worlds, the wandering trader spawns in fine, but it is only on my old world where I am yet to see it.

This is mostly important to gain the small drip leaf and the big drip leaf item.

Additionally (might be interesting) until 1.17.10 I didn't see any pillager patrols roaming around and coming to attack me. Similar again in old and new chunks, but this seems to be working again now. Not sure how much the spawning is related, but it seems to be quite similar.

The wandering trader bug also affects 1.17 and 1.17.2.

Thanks!