Fecal Float verse Fecal Smear

My cat Sophie is about a year and a half old. I always thought she seemed kind of thin. That combined with noticing her pooh wasn't quite right, I took her to the vet. Turns out she was fine and we can solve her feline irregularity with Activia. They prescribed a low dose antibiotic. I'm not sure why they couldn't have prescribed a trip to the grocery store to pick up some yogurt, oh well. I was looking over the bill when I got home and saw that not only did they do a fecal float they also did a fecal smear. Now really, is that necessary? In all of my trips to the vet they always do a float and I've never seen a smear.