Because I dislike most "fantasy" races.
And I'd keep both Aasimar and Tieflings.... since both are technically human.
I might keep one of the dwarven and elven races, Wood Elves and Gold Dwarves... but all others would be removed.
Also there'd be NO gnomes or halflings. At all.
I tend to like things a bit streamlined, rather than having dozens upon dozens of different races/monsters. Not to mention an endless horde of "humanoids"
If I could figure out how to make my own races, I'd probably convert a few monsters into playable races.
As for classes, I'd keep them basic. Barbarians, Rangers, Fighters, Clerics... of a sort, Druids, Rogues, Sorcerers and Warlocks. Maybe wizards, but the rest wouldn't fit what I have in mind.