You walk into whiterun, steal some stuff, get a bounty. Now at this point you feel the best thing to do is RUNNNN. I can understand going back to whiterun and someone saying " Hey look, Its Mr. Shenanigins wearing a thieves guild armor and a wooden dunce cap that stole stuff earlier, lets get him." So how come i can't go back dressed in full mage robes and a krosis mask and not be recognized? I mean isn't part of a hitmans/assassins/thief/con artists repertoire, the ability to change appearance to avoid suspicion?

Game logic

ok.

Its your scent. You smell like a sneak-thief, you milkdrinker you.

It's because you gleam like fresh fallen snow and you clank like a kitchen.

Nonono, that is the Legion. The Thieves Guild just look really shady and the Mages who are Theieves Guild look like they are trying not to be shady

Disguises are something I've always thought were missing from Skyrim - along with a suspicion meter and guards forcing you to reveal your identity if your suspicion level gets too high. Would've added more depth to the gameplay.

Disguises have been use in the past in these games. Some quests in Morrowind required a disguise to complete them. It would be easy to add the script that adds the player to the faction while the clothes are on. Problem is, how do you make it so the NPC could detect you if you do something out of character? That's where it gets a bit complicated.

So much this. I mean if they have a whole questline dedicated to thievery why not add this element