Apart from the artistical question if we even want more "dirt" in our games, it's also a more mundane question of complexity and effort.
Lets take the example with a marketplace, where there could or should be more stuff on the ground, including, but not limited to dirt. That's not easy.
I many years ago had a talk with a 3D artist who said that's it's a simple thing to make a scene, e.g. a set coffe table with a cloth, some cups, a pot, and a fruit bowl.
But now if you want to add a drop of coffe that's sliding down the pot, a coffee stain on the cloth, a small crack in a cup, and some dark spots on the not-so-fresh fruit, it get's complex.
I guess it's similar for "dirt in a medieval world" in general.
Lets take the example with a marketplace, where there could or should be more stuff on the ground, including, but not limited to dirt. That's not easy.
I many years ago had a talk with a 3D artist who said that's it's a simple thing to make a scene, e.g. a set coffe table with a cloth, some cups, a pot, and a fruit bowl.
But now if you want to add a drop of coffe that's sliding down the pot, a coffee stain on the cloth, a small crack in a cup, and some dark spots on the not-so-fresh fruit, it get's complex.
I guess it's similar for "dirt in a medieval world" in general.