It does seem there are two camps:
1. We need a baseline. It should be clear it's just a baseline and subject to variation, and it should be well-done (interesting, not racially insensitive, etc), but without one the entry isn't fully usable.
2. We should not have a baseline, but several brief suggestions and have the dm's fill in the details as they see fit. This avoids any sense of the baseline being seen as 'canon' (because some people will see it that way no matter how many times you tell them not to) and prevents any sense of monocultures because there's clearly more than one culture here.
The "why not both?" argument is the page count would get crazy if we included multiple complete cultural descriptions, meaning the MM would need to be huge and/or contain half as many monsters.
(Spitball idea: maybe it would be better to pick 2-5 "core" monsterous races and just -not- include obscure ones on the main MM. So orcs, goblinoids, lizardfolk, something that swims, giants of several sizes, maybe drow, and everything else can come later?)