STEM degrees are more difficult than humanities/arts degrees.
Firstly I have about 24 hours of lectures and labs a week, my housemate studying Politics has 8, with 2 days off in the week. And before anyone jumps in with the whole we have to read stuff argument, SO DO STEM students! Independent study, lab reports, coursework the bloody lot! There's no way that the independent study done by the rest adds up to what we do. It may appear you have as little time to do stuff as us but that's just because you're in bed for 15 hours a day and watching Netflix. I have 5 8:30am starts a week, a friend of mine doing English has zero, his earliest is 10am. It's a joke.
I can appreciate that they have their need in some places and they aren't exactly a walk in the park, but they certainly aren't even.