Why don't theme park restrooms have mirrors?

Vandalism.

Robert is exactly right. Mirrors are especially susceptible to vandalism for a couple of reasons. There are no cameras observing the insides of restrooms, so someone who wants to put a tag in the park has the perfect location when things are slow. The vandalism we experienced at the Rest Rooms I was responsible for weren't tagged with ink or paint, the person used glass etching chemical. It can be loaded in a pen and it creates a scar on the surface of the glass that is permanent. The only option is to remove the mirror. The mirrors in the restrooms at Universal Orlando were massive, covering most of the wall over the sinks. It costs thousands of dollars just for the mirror, not including the labor involved to remove the old and install the new. It's just not an expense that is worth the money.

Most illuminating, as that's something I've often wondered myself. Vandalism never occurred to me; I thought that maybe it was a penny-pinching measure. At Six Flags Great Adventure the restroom immediately inside the gate has mirrors but the others do not, so that's the one I have to use to apply sunscreen to the tattoos on my back - as I really need a mirror to see what I'm doing. I don't usually apply makeup at a park but this would indeed be challenging.

I've always thought that Disney didn't install mirrors above the sinks to expedite guests' trips to the restroom. Most Disney restrooms (and many Universal ones if I recall) have a single large mirror near the exit where guests can check their "A, B, C's" so they're not standing in front of a sink. Putting the mirror by the exit reduces the time people use it because they're naturally blocking the flow of traffic and will quickly take care of their business and make their way out the door.

I can see the point regarding vandalism, but I think that's an issue with any bathroom fixture, and always considered the dallying while preening in front of a sink mirror a more logical reason for a lack of restroom mirrors.

I'm curious now-- do restrooms at the Disney theme parks have mirrors? It's just in the last few months that I noticed the situation at Universal and Knott's, so I can't remember.

If Disneyland and other Disney parks do (and if the issue is vandalism), are visitors better behaved at Disney parks, or do they have better security there?

I can understand no mirrors in restrooms in a public beach or park, but they do have them at places like the Huntington Library, the Getty Center, most museums, county fairs (if I remember correctly).

I can't understand that theme parks are more of a target for mirror vandals than any other tourist-centered location.

I haven't been to the California parks in over 5 years, but I can confirm that all of the Disney and Universal restrooms in Florida have mirrors. However, there is typically just a single full-length mirror located near the exit (sometimes another mounted above or near the baby changing station), and none located above the sinks. In fact, one of the newest restrooms at Universal Studios (near the Jimmy Fallon Ride) has more modern trough-style sinks facing each other (instead of against a wall), so there's nowhere to install a mirror above the sinks.

Most other theme parks around the country have mirrors above the sinks, but a few have gone to the single mirror near the door and none above the sinks in high-traffic restrooms.

The parks at Disneyland resort all have mirrors. I thought Universal had single large menu near the entrance / exits.

Seaworld restrooms all have mirrors too .... Some over the sinks and others on the way out.
Never thought I’d be writing about mirrors in restrooms on TPI .... :)

I've truthfully never paid any attention to this, but now I'm probably going to be on the lookout the next time I visit a park. I wouldn't be surprised to find that it varies from restroom to restroom within the same park. Other than SFMM (which I don't believe has any mirrors), I seem to recall some sort of mirror in at least some of the restrooms at every So Cal park.

I asked this on a fb forum, and a Knott's employee who works in the restrooms said that it was essentially a safety issue. To prevent people from breaking the mirrors and to prevent them from writing on them.