I understand there are jobs that have you on the go, and sometimes, that can make it hard to attend to personal things, such as peeing. After all, it sort of made sense to me that the astronaut would want to limit her stopping on her way to convince someone to love you instead. (Time is clearly of the essence there. Of course.)
And let's face it, some highways (NJ turnpike anyone) have their exits twenty seven miles apart so you may hit a critical phase bodily-function-wise and have a ways to go.
However, there are places where it would be disgusting (or more disgusting) to spit, much less pee. And if your job takes you to one of those places, well, you may wish you had a diaper. And if you don't you just have to wait. Say, for example you were a press photographer, covering a funeral for a soldier. The call of nature can be hard to resist, but when you are on the job in a cemetery, resisting is the best action. Especially when your fellow photographers are there to photograph you relieving yourself.