Don't know about other people, but when I dream about having to go to the bathroom, it's because I have to go to the bathroom in real life.
For most of my life, these dreams took a predictable form. The need to pee would become the most important concern in the dream, but invariably, all I'd be able to find would be the world's dirtiest bathroom (Trainspotting style). But then on top of that, the door won't close, or there are no doors period and tons of people (including men) around, or the toilet is up on some kind of platform that I have to climb up, or I have to stand on a platform and aim and pee down into a toilet from far above. And I'd try to go, but not be able to release, and then I'd wake up.
I always used to think, if I ever did actually go in my dream, that maybe I was wetting the bed. Well, recently, the dream goes exactly the same way, but I do actually start peeing in the dream. The last one a couple days ago involved aiming for a little bowl from a high platform under the watchful eye of a mean old Chinese cleaning lady. I did start peeing, an no, I didn't wet the bed. What happens now is that I can't stop peeing in the dream. So I wake up mid-pee.
Is it age? What's next for me in the world of pee dreams? If I stop peeing in the dream, does it mean I've wet the bed? Is the next milestone total incontinence?