The Tavern

I will often switch between functionally identical robe and cloak types if I find one I like; the good ol' black on white is my favorite. Sometimes I mix it up a bit and go for a dark blue robe, but that's just if I'm feeling feisty. Pink doesn't go well with much, but there's nothing like following Makhleb while clad in pink, so death gods will have to put up with my fashion statements.

How about you?

When I played TrBe I would swap robes obsessively like a high school girl, keeping fancy ones around in case I changed my mind while away from the stash.

I will spend a couple of hours over the course of a game making the perfect ensemble for my character. Generally my assassins tend to hang out in greys and blacks. My ice magi tend to end up in white cloaks and blue robes. My fire magi normally end up in black cloaks and red robes. Summoners always wear yellow clocks and yellow robes. (Because only a coward would travel with a bodyguard of three or four dragons.) My air magi tend to end up wearing light-blue cloaks and dark blue robes. Necromancers and necrusaders normally wear black robes with dark red capes, not cloaks. Healers end up all in light-grey, not entirely sure why. Hunters get a green cloak and if a troll or ogre or spriggan a brown robe.
I also change my outfit to match the scenery if I'm a class which I imagine as being stealthy. (Hunters and assassins) Lair? Greens and yellows. Vaults? Silvery-light-grey. In Zot I change my attire to match whatever the walls are coloured as. Tomb? Browns and greys. Cocytus? Light-blue and white. Gehenna? Red. Dis? Same as vaults. Tartarus? Greens and blacks.
Yes I am somewhat crazy about this. Yes it wastes time, turns and consumables. But I'm always going to keep doing this because it's fun to have a character to actually blends in with the tiles.

why not just edit the player doll?

It's actually quicker to just put on another robe.

Not everyone is playing offline, either.

and if you are playing offline, editing the player doll will annoy your other characters, who didn't mean to put on skirts.