Honestly, the unsatisfying answer is simply because they (i.e. those of us who didn't grow up on IRC, like marketing teams) want to, and are used to being able to do it elsewhere. I'm sure the people who include images in email and set their own fonts and stuff are happy with the upgrade; I can especially relate to that since I used to do some marketing and sales work myself.

I also hate the new input field but I understand why they turned it on globally. But a strong enough want is often indistinguishable from a need.