Delicious In Dungeon / Danjon Meshi - Come to Dungeon Meshi, we have:

And, according to omake (which I'm told is called Adventurer's Bible now), even Laios' ultra generic looks is a significant part of his characterization.

Long story short read it yourself for details, he's usually unshaven and unkempt until Falin told him he's starting to look like a certain someone. Bath, shave and haircut ever since.

Theory ? That's canon