Practicality in clothing revolves around weather and temperature. Thick clothes for cold spells and so on. Deer put on lots of extra layers at the first signs of cold weather. Lately they've not been needed. So the scruffy appearance could mean a moult. Alternatively it could mean simple wear and tear from movement through wilder parts of the woods. It's unlikely to be a human-inspired fad such as that for designer stubble.
But of course it could be the result of too much of this.
Why restrict the pleasures of a good scrap to the rutting season?