For those who are not familiar in Email's CSS support, Gmail is actually a blocker, not a mover: https://www.campaignmonitor.com/css/
You say that like it is a bad thing. I'm really pleased that email cannot set a style header and has limited ability to have the email deviate greatly in presentation from other email I receive.
If you want to show your styles to Gmail users and you have to inline your CSS in every HTML tags you want to alter, which is very ugly and made the email size unneeded large.