As a DM, I just cannot be bothered to roleplay countless unimportant NPC-encounters where yet another bunch of villagers scratch their heads why a Tabaxi, a Kenku and a Tortle walk through their town. Also, of course every person on the continent will remember that party, so the party can forget about traveling inconspicuously.
If the campaign setting and story bores the players so much that they must make the campaign interesting by playing some exotic race from a non-core book, then that's a reason to see how the campaign setting can be improved.