Couldn't someone anyways display the content on one screen and take a photograph with another device. For text content, the degradation of image quality doesn't even matter. Doesn't that make screenshot-blocking a pointless exercise?
Of course they could, but you reduce the probability that any random person can do that by taking precautions. Screen photographs also betray information that screenshots don't, for example nearby surroundings where the photo was taken, any reflections on the screen which may show who took it, metadata that can be used to conduct forensics to figure out which device took the picture, etc. In order to avoid giving yourself away, you'd actually have to plan a photographing mission, which may be made impossible by the circumstances (e.g. the device is held in a room with security cameras, nearby coworkers question why you're taking pictures of documents on your screen, your workplace may not allow secondary devices past the entrance, etc.)
Whereas with a screenshot you just hold two buttons and you now have an image that you can exfiltrate through a variety of ways into the hands of the bad guys.
There are also legitimate reasons for blocking the disabling of location services. If I have devices with proprietary applications or access to proprietary data sitting in a secured room, I want to make sure nobody can take that device out of the room, and if they do, the device should enter some sort of lockdown or sleep mode so as to prevent the leaking of sensitive information. This is a legitimate feature that would make sense to implement on commercial (not consumer) devices. That the OS ships with the ability to disable disabling location services is not an indictment on the OS - it is only an indictment if the OS does so without your permission.