Allow dedicated CSS files, and Insertable Divs

I agree, not being able to create your own or edit the existing site css files is huge step back for the professional site designer/developer. Google “Rotate an image on hover using JavaScript”, and you will be lucky to find anything, and if you do, it requires a fair amount of coding and multiple images. I can do this simply in css using the following:

img {
-webkit-transition: -webkit-transform .8s ease-in-out;
transition: transform .8s ease-in-out;
}
img:hover {
-webkit-transform: rotate(360deg);
transform: rotate(360deg);
}

Why would I want to do more work than I have to? I can see using WiX for a very simplistic site, but Not being able to edit css for a site is kind of a deal breaker for me.