Have you ever tried to get a urine sample from a dog? It's very hard.
Our dog was sick one time and the vet said to bring in a urine sample. So you take the dog out, and it's unpredictable when she's going to pee. You're there with a little plate, trying your best not to freak the dog out, who of course has no idea what's going on.
Then when she drops down to pee, you can't see what's going on down there because of the overhanging fur, so you try to shove the plate in, further confusing the dog who instantly quits peeing.
By now she's looking at you with a mixture of confusion and distrust. "Are you angry at me for some reason?" she's wondering. So you say, "Good girl, everything's good." Finally you win back her trust long enough for her to try to pee, and you shove in the plate, which this time comes up with a dribble, probably not enough.
Your temper is rising because we could be doing this all day, squat and shove in the plate, and it's not going well. The more you do it, the harder it is.
Finally we got several more dribbles, enough for a microscope, I guessed. And the vet said that was enough. Good job.