Because it skips step.I'm still trying to figure out how "no yuan-ti" equates to "viking hat railroad GM" tho.
The "Why do youwant to be a yuan ti purebrood?" step.
Because based on the answer, the DM can offer a race, class, feat, item, curse, or boon within the setting that gives the player that.
If the answer is something commonly found in D&D but not an aspect in the setting, the DM's setting might too narrow.
If the answer is something rarely found in D&D and not an aspect in the setting, the Payer's desire might too narrow.
D&D is a rather conservative game in 5e. Most of the racial aspects exist elsewhere. You can usually fiqure out who is being unreasonable based on the "Why" question.