WHY do dogs do that....UUGGHH

I actually know WHY they do and haven't had the time to take Roxy to the vet to get yes the anal gland drained........... We were out of town (up in seattle and I promise i looked for the camera to take pics and put on here but i couldn't find it ;0( ........ anyway I picked up roxy from our good friends who watch her when we leave and she had a little bit of poop on her butt and NO ONE wanted to giver her a bath SO this morning i got sick and tired of her scooting her butt across the floor ( I THINK THAT IS SOOOO GROSS ) AND know i want the carpets cleaned even though i don't see anything i KNOW it's there.... so yes this morning after dropping brax off at BBALL tryouts i actually had to wipe her butt with a baby wipe. UUGGHH