In my experience lexers and parser generators are used extensively by hobbyists. Tools such as Antlr, Boost.Spirit and Xtext come to mind.

Xtext is very marginal compared to the far wider world of custom languages. Antlr not so much, but still, tons of people write rec. des. parsers themselves.

Is that true? At least in the OCaml ecosystem (where there is many many compilers), ocamllex and menhir seems to be used quite often.

I know a lit of hobbyists and professionals who just roll recursive decent parsers given the reduced complexity and better error recovery. Using these tools, they don't necessarily help unless you have icky syntax to deal with or really care about that last ounce of performance.