I think a lot of people have a slightly skewed idea of what "useless" means.
I regard very little of the knowledge that I have acquired "useless". Why? Because even though a lot of it doesn't exactly have a practical application, it has given me a more rounded world view and makes me more interesting to talk to.
For example, knowing about WW2 may not exactly help you in day to day life. On the other hand, if someone told you they didn't know who Winston Churchill was, you would think that they were a darned idiot. On top of that, knowledge about WW2 has shaped my opinions about people, war, politics, economics and philosophy. I could say similar things about my knowledge of science, maths or philosophy. I'll never be in a situation where knowing how to measure the speed of a star will put food on the table, on the other hand, when I'm with someone looking up at the sky, we can discuss how we know so much about stars and the implications of the big freeze\crunch theory. Also, good understanding of the scientific method means I'm unlikely to be taken in by pseudoscience. If I choose not to go into a career in science, that probably won't ever be "useful" in the same way that knowledge of electronics is useful to an electrician, but it is useful in countless other subtle ways.