It's also a problem of how much you can ask a student to do. There was a time when the expected time to complete a "4-year degree" was approaching 6 years in the engineering-ish fields, and the tuition-check-writers got pissed and called their state legislators to put a stop to it. So adding some sort of multi-semester capstone project would have to be woven into what is already in place, but I would imagine it wouldn't entirely fit into the curriculum without increasing the student level-of-effort (meaning, all of the stuff being taught would still have to be taught, but in addition the extra bits special to the scale of the project would add to the overall workload).
It wouldn't have to be that big. Even if part of one semester was to take a month as a class and try to add some features and fix some bugs to a codebase that the previous decade of classes had worked on, that would be an eye-opener to most students.
