Should I buy a 3d printer?

The short answer for many people is "No". The normal house wife / man very likely do not know much about a CAD/3d-program and doesn't have the technical Know How you may need to operate those machines.

For do-it-yourself people and enthusiasts with a little technical talend I would say: If you want one, get one :). As a big-boy toy a 3d printer is still quite expensive but not that much anymore. Some devices are already available for a few hundred bucks and the costs are still going down. But those very cheap once often need more experience or at least will to get them to work right.

The right answer is: If you find it interesting to work a little with your 3d printer and sometime find solutions for smaller problems and just fiddle a little bit with it, a 3d printer is something you will love. It can product really great stuff if you have enough talent and you certainly do not need any kind of diploma to create those small gifts, toys, replacement parts or even own designs.
Just don't buy one if you are just after the end result. You need to have fun on the way too, otherwise it is not worth it.

Because of that many scools have started buying those devices for pupils who want to do it in special work groups and give them the possibility to create things, which never ever before have been there. But you will have a hard time to find them in the "default" subjects. Those are special interest work groups.