To be honest with you, I've never been sure why orcs aren't subtype goblinoid. Although there's too many humanoids by far as it is.
Weren't they originally? I think that orcs were originally "lumped in" with the goblinoids--I recall that half-orcs in previous editions could also refer to any orc/humanoid mix, such as orc-goblins, orc-hobgoblins, etc. IIRC, the old "grey box" Forgotten Realms set used to list orcs with the goblinoids. But then again, these were also the days of Lawful Evil orcs, kobolds & xvarts being related, and the "giant class" monsters for rangers.
I have to agree with you, as well: there ARE too many humanoids (for my tastes, anyways). Many monsters (esp. humanoids) seem to be different variations on the same theme, with slight stat changes (possibly in order to "keep the players guessing"). There seems to be quite a large number of synonym-based monsters in D&D though.
I'm not crazy about it, but then again, it doesn't stop me from using them all, of course.

Then again, for the most part, I avoid racial variants (like grey elves, grey dwarves, forest gnomes, etc.) completely. IMHO, there's enough synonyms & slight variants going around D&D as it is.