It's a problem. Until people have standardized on which 'better standard library' to use, programs will keep building from these too low level building blocks.
You look at some random OCaml code, and it looks like this:
when String.length line > 4 && String.sub line 0 3 = "+++"
I hesitate to answer your hyperbole about ten variants of equal signs. It's not uncommon for languages to have two notions of equality like ocaml has (or even more): Here's Python for example: http://stackoverflow.com/questions/132988/is-there-a-differe...
To answer your original question of why anyone would prefer to not use startswith: I don't think anyone does.