Because they didn’t actually live in caves that often.

The image of these people living in caves arises from the fact that caves are where the preponderance of artifacts have been found from European Stone Age cultures. However, this most likely reflects the degree of preservation that caves provide over the millennia, rather than an indication of them being a typical form of shelter. Until the last glacial period, the great majority of humans did not live in caves, as nomadic hunter-gatherer tribes lived in a variety of temporary structures, such as tents[4] and wooden huts (e.g., at Ohalo). A few genuine cave dwellings did exist, however, such as at Mount Carmel in Israel.>

Wikipedia - Caveman

You could post a bug on the Jerboa community. It might be known and have a fix out soon. I think most apps have their own quirks. Either way, let me know if you have any success.

I also don’t get them on Jerboa. What instance are you on? I think that communities wont show up in your instance unless someone has already accessed them. If you search directly for the ones in the post above, they should show up. I think you have to put an exclamation mark in front of the term. E.g.
!weather@community.xy

Hope that works.