True, but here's the thing. By the time a Waterloo student has had 3-4 co-ops, the co-op program needs them more than they need the co-op program.

It's trivial to switch to non-co-op Computer Science. The co-op program admins try to guilt you out of it, but there isn't any real penalty.

The admins want to keep upper year students in the program to attract companies, since companies often want to hire more experienced interns.

Why do students drop co-op in later years? The co-op program costs extra (~$1500/year). There's some more or less useless professional development courses you must take, as well as reports you must write after 5/6 terms. In other words it can be a somewhat expensive hassle.

Maybe the one thing the co-op program can provide is they help with J1 visa to the USA. And tax incentives for Canadian companies to hire interns. Those benefits often aren't enough of a draw for someone who has 1+ years professional experience at 3-4 companies.

Hence, what often happens is that upper year students drop co-op or go outside the program to find internships. They find their own jobs, in some cases the company arranges the J1 for them.

For example this term, a bunch of Waterloo coops wanted to go to SF, but the coop program wasn't offering positions which required travel to the USA due to covid. They just made arrangements with the companies directly.