Let's say you have every monstrous race in the book, along with every possible PC race. Where do they all get their food from? There's only so much arable land, they can't all live "in the mountains". Even if you assume magical food sources for underground (I do to a certain degree), there's a limit to population density of relatively large species.
Some of it may depend on how genetics works as well in your campaign. Can a race continue to exist if there are only a few dozen members of the species? Inbreeding will kill off a species after a few generations. I'm assuming we're all familiar with the whole "last of my species" trope, but how long does that last? One generation and they're gone.
I just find it hard to find room for a sustainable population of all the following humanoid races:
Which is not the only reason I limit races, as I posted above.
Some of it may depend on how genetics works as well in your campaign. Can a race continue to exist if there are only a few dozen members of the species? Inbreeding will kill off a species after a few generations. I'm assuming we're all familiar with the whole "last of my species" trope, but how long does that last? One generation and they're gone.
I just find it hard to find room for a sustainable population of all the following humanoid races:
Aarakocra, Aasimar, Air genasi, Aquatic elf, Avariel, Bugbear, Bullywug, Deep gnome, Deep scion, Derro, Dragonborn, Drow, Duergar, Dwarf, Earth genasi, Elf, Firbolg, Fire genasi, Firenewt, Flind, Forest gnome, Genasi, Ghostwise halfling, Giff, Gith (race), Githyanki, Githzerai, Gnoll, Gnome, Goblin, Gold dwarf, Grimlock, Grung, Halfling, High elf, Hobgoblin, Human, Jackalwere, Kenku, Koalinth, Kobold, Kuo-toa, Lava child, Lightfoot halfling, Lizard king, Lizardfolk, Locathah, Meazel, Merfolk, Mongrelfolk, Moon elf, Nilbog, Orc, Orog, Quaggoth, Rock gnome, Sahuagin, Sea spawn, Shadar-kai, Shield dwarf, Skulk, Star elf, Strongheart halfling, Sun elf, Tabaxi, Thri-kreen, Tiefling, Tortle, Triton, Troglodyte, Urd, Verdan, Water genasi, Xvart, Yuan-ti pureblood, Zerth
Which is not the only reason I limit races, as I posted above.