One of the reasons for not adding new races to the PHB is WotC want to sell supplements. You are not intended to be locked into core rules content, you are meant to spend money and buy additional stuff. Otherwise it's impossible to make a sustained profit.
And yet, we
still (as shown in this very thread) get people complaining about how gnomes, the least popular of all "core" races, got shifted to PHB2 in 4e. Even though other highly popular options also did (Sorcerer, Druid, Barbarian, Bard, devas which are essentially aasimar, half-orcs), and you never see folks complain about that, or at least I haven't.
Because the issue isn't whether something
can be played. If it were, 4e would never have gotten the hate it did.
Instead, the issue is (and has always been) twofold:
- Are the options I identify as critical enshrined in the PHB?
- Are the options I opposed as badwrongfun excluded from the PHB?
Being present in the PHB is, in effect, seen as canonization by WotC. It's validation, even promotion. Anything in the PHB is "real D&D," and anything outside it is demoted to some lower tier, second-class status. Hence why the so-called "exclusion" of gnomes was a problem (even though, in 4e,
everything is core, at least if it's official content), and yet also why the 5e
inclusion of dragonborn was a problem. The former was seen as shouting from the rooftops, "this thing a small group loves ISN'T D&D!" And the latter was saying that people who find dragonborn annoying or grating are wrong, because it's just as much D&D as elves and dwarves.
The issue is whether "I got mine and made sure others didn't get theirs." It saddens me greatly to see it laid out so clearly, but there really isn't another explanation here for the intense and sustained yet seemingly contradictory responses.