Why shouldn't all savage raids drop mounts?

[EaMett]

yea but people always start raiding at different times, at this point i could see no reason to run the other 3 ¯\_(ツ)_/¯

That's the point. We're in the catch up part of the patches where the game allows people who don't run savage content to get their gear.
It isn't a flaw, it's the design.
The incentive for everyone else is that you can now farm the content to get your BiS on other classes (if you're into that), you can challenge yourself against some of the harder content in the game, and you can get a mount in the last floor.