What would be the reason to say no to any race?
The more the better! Allways and every single time.
The reason is simple... some among us, like me, don't like to see monsters become player races. And yes, for me even Drow and Duergar are already pushing it.
Why can't people just play an ordinary elf, halfling, gnome, dwarf or human? Why does it have to be something outlandish like Tieflings or Dragonborn or even worse, a monster race?
Yuan-Ti are monsters for a reason, same as goblins, kobolds and every other monster race someone may ask to play.
