I disagree. As an undergraduate, I majored in physics, and had a strong math minor. However, I was required to take quite a few liberal arts courses. At the time I didn't see the need for them, but since then I've been glad I took them.
Yes, I've done a lot of reading in history, government, economics, etc. since graduating. However, there's a big difference between simply reading something and having an instructor who knows the topic guide you through it. A good instructor already knows what the alternative views are, and can make sure you see all the important ones. Some things are obscure (just as they are in physics or math), and an instructor can help you through those. As an example, about 20 years ago I was dating an English professor. In an effort to please her, I drew out from the library a book by her favorite poet. I had a terrible time with it. She led me through some of the poems line by line, explaining the obscure references and how the poems related to other poems by other writers. I'd never have gotten that without her help.
I would argue that students in STEM majors need the arts -- history, economics, literature, etc. -- in order to understand the culture we live in. Moreover, they can't "get it" by just reading, any more than they can get through a calculus textbook without the aid of an instructor. After they've been properly introduced to the arts, yes, they can continue on their own, just as STEM graduates are expected to continue their development by reading the technical literature of their field. But they need the basic understanding that only an instructor can provide.
You forgot the sarc tag.