"Working for free" after 40 hours isn't necessarily accurate if you are on salary, at least if your company is run reasonably well. At my job, I'm paid a salary based on my performance and the quality of my deliverables. If I finish those in less than 40 hours, I am free to go home (although I generally stay and get some work done on projects that are less time sensitive), but if I have to stay late to finish them, I may end up working more than 40 hours. Nowhere in my agreement to come work here was 40 hours a week specified. If it became the norm that I worked 60 hours a week to complete my deliverables (and I wasn't sandbagging), I would ask for a raise to reflect that.

However, I agree that many companies are not great at this. While my company is not perfect, their handling of this issue is one of the many things they do extremely well.