I honestly never sent my daughter to daycare in a skirt or dress for that reason. Although, I must confess I am pretty much a tomboy and very rarely wear them myself. I also hardly put dresses or skirts on my daughter in the winter due to the cold (she hates tights) or in the summer. I find they get in the way of her playing (especially when she was younger and learning to walk).
I do have a dcm who sends her daughter in nice clothes constantly, but I let her get dirty outside. I do not change her clothes as I don't have time and if the mom wants her to wear those clothes to daycare, I assume she does it knowing that they will get dirty.
I suggested to all my parents that they get splash pants for their kids, but no one has complied yet, so until then, they all get dirty outside.