There are many of these. And they mean it. If you put them in the dishwasher, they will leak and have condensation problems and be generally gross.
How does this make sense? This is something you use every day. You probably don't want to wash it by hand every day. It goes without saying that you probably don't want it to produce its own ecosystems.
I have one. It has pink alligators on it, which is great. But I have to scrub it every day, which is not.
The worst part is that, by owning one, you are reducing waste, which is (indisputably) a good thing. But you are at the same time slowly losing your mind. So...toss-up?