I dislike the inclusion of tieflings as a core race in 5E for the same reason I did in 4E, it's not a classic archetype (even by D&D standards) but a world-specific one, and as such it belongs in the sourcebook for that world or briefly summarized in the MM rather than the core player rules. Ditto dragonborn.
I mean, I'm the guy at the table who always wants to play catfolk, wolfen, or even gnolls, but I know they're outliers. And as such, they don't belong in the core book. A brief writeup in the MM for "_____ player characters" should be enough.
-The Gneech
They're only not a "classic archetype" because they haven't appeared in several books previously. But just wait. Once 8E comes around and tieflings will have appeared in four editions previously... at that point they'll also be considered a "classic archetype", the exact same way the half-orc is now.
But by clinging to the idea that you can only include races in the Player's Handbook that have appeared in several previous Player's Handbooks... means that we'll never see any changes to the races of the Player's Handbook. And that's kind of lame, if you ask me. I mean, if we did that with classes, we'd never have the Barbarian, we'd never have the Warlock, we'd never have a Bard that wasn't some weird multi-classed prestige class.
Books change. Attitudes change. New stuff sometimes gets added, old stuff sometimes goes away. That's the way it's always been, that's the way it'll always be.
