I remember that I was using trees quite often last century, when I was writing programs in C. I seldom use tree or comparably complex data structures nowadays,

I remember that I was using trees quite often last century, when I was writing programs in C. I seldom use tree or comparably complex data structures nowadays, when I almost only write web apps (mostly backend in Ruby or Python but some frontend in JS.) I'm bet that both Ruby and Python have plenty of trees written in C inside their interpreters. I do everything with arrays (lists) and hash tables (dicts) in Ruby and Python. Maybe a language construct for trees would be nice for lower level languages and almost out of scope for higher level ones. The same from another angle: there are a lot of trees in the indices of SQL databases (example [1]) but we don't zoom in to that level of detail very often when defining our tables. [1] https://www.postgresql.org/docs/current/btree.html https://www.postgresql.org/docs/current/btree.html