Edit of css general and index

I just want to know why we can't edit the css general and index direct in the admin control ?

As for me, both general.css and index.css are listed in Admin Panel - Settings - CSS Styles Editor... (Dolphin 6.1.1)

Yes i know, but i have this error message :file general.php is not writable

I just really understand that I have not put chmod (R/W/RW) for this file... so it's ok.

Thanks for your time and your answer.