I'm in the US and my parents paid for my college/university. I had to work part time to pay for socializing, car, cell phone, etc... Most of my friends either had a work study or part-time job. I also did have a lot of friends who had to pay their own way through school and had to work part to full-time while taking classes.
DB goes to Uni in England. Most of his friends don't work, if the work, it's only about 6-10 hours per week. DB only worked during the summer until this past year and he worked part time after school. He has done student loans and overdraft. His parents have given him £30/week to pay for food and whatever is left he can use for socializing.
I agree that it usually just takes time management to be able to work and go to school. I know some degrees may be more time-consuming than others, and that can even fluctuate from semester to semester. For one semester of my course, we were strongly advised not to work, it used to be a requirement, but with more people paying for college on their own they felt they couldn't ethically enforce that any longer. One year I worked 30 hrs/week at one job, 10 hrs/week at another, and took 5 classes. I would not recommend doing that, but I got through it and I know people who had to work harder than that!
I think most people would prefer not to have to work while going to school, but I think most people could find a way to make it work.