This is because R borrows a lot of syntax from S. When R came out, statisticians were using S, so it was natural to make it like this. If they went another way, you'd get statisticians in mailing lists 20 years ago bemoaning how its so much not like familiar S, rather than regular old programmers 20 years later today who bemoan that R isn't like familiar python like what happens on HN whenever there is an R thread.

Idiosyncrasies are not something unique to R.

One could express the same surprise at an empty list being considered false in some contexts.

As far as weird edges go, that one is really, really mild. It may even be considered a good idea!

For people interested in weirder things, check The R Inferno (I think it's somewhat outdated by now, though):

https://www.burns-stat.com/documents/books/the-r-inferno/