Sonic and friends have absolutely never fucking ever been fur-shaded, and as technology has progressed the respective character designs have not changed significantly in a more furry direction.
Some characters have tufts of fur on their sprites in the 2D games, but in the 3D games the characters still continue to look like they're molded out of plastic and/or rubber.
The deal is they aren't supposed to look realistic and Sega already gets the furry tismbux, so they have no reason to go further.
Noah Jackson
Some examples of characters that are clearly furry animals
Jordan Hernandez
The characters are more fuckable that way.
Grayson Phillips
Too much realism is often a bad thing. In the case of Sonic, they're probably also taking into consideration that the characters are going to be moving very fast so their designs need to stay clean, and that too detailed fur could potentially tank the framerate.
Leo Brooks
Post porn.
Thomas Cox
And it always looks uncanny as fuck. Only one of those it works with is DK, but that's because he barely has any cartoonish elements and looks mostly like a regular ape.
Justin Johnson
This user has the right idea
Jose Peterson
This art is pretty damn subpar.
Nolan Carter
Hair physics do retarded shit at high speed. And if it didn't move at all it'd look even worse.