I see your point about education. Everything has its place and a for loop can sometimes be easier to read. But some algorithms are more naturally expressed recursively.
A lot of languages do support TCO. For example, Scala (used by Twitter), OCaml (used by Jane Street for everything, used as the host language for Coq, originally used to implement the Rust compiler), Kotlin, Haskell, Clojure, Lua (used as an embedded language in many places), Elixir, Perl. Not necessarily your popular bread and butter languages but definitely used in production and available if necessary.
Your point that it is generally difficult to know whether TCO is applied is also well-taken. But in OCaml, you can annotate the recursive function call with `[@tailcall]` to verify that the compiler performs TCO.[1] Likewise, you can annotate your functions in Scala.[2] In languages without such annotations, one can get a sense by memory profiling (possibly not emphasized enough in those intro CS courses).
A lot of languages do support TCO. For example, Scala (used by Twitter), OCaml (used by Jane Street for everything, used as the host language for Coq, originally used to implement the Rust compiler), Kotlin, Haskell, Clojure, Lua (used as an embedded language in many places), Elixir, Perl. Not necessarily your popular bread and butter languages but definitely used in production and available if necessary.
Your point that it is generally difficult to know whether TCO is applied is also well-taken. But in OCaml, you can annotate the recursive function call with `[@tailcall]` to verify that the compiler performs TCO.[1] Likewise, you can annotate your functions in Scala.[2] In languages without such annotations, one can get a sense by memory profiling (possibly not emphasized enough in those intro CS courses).
[1] https://v2.ocaml.org/manual/tail_mod_cons.html
[2] https://www.scala-lang.org/api/2.12.1/scala/annotation/tailr...