There is an advantage of "baby's first introduction to the idea that different peoples can have different cultures, and they're all valuable." - for some people they've never experienced or ever thought about this... and it's "simpler" to grasp than (the much better design) of different regions having different cultures, and each region having a mix of races.

On the other hand, there's a massive disadvantage in portraying "all people of this race are (stereotype x), all people of that race are (stereotype y)"

DMs and GMs, this is a place where you can shine with your worldbuilding. Make towns that have a mix of races, and give towns their own culture. It's worth it and much more immersive.