CEGEP provided an excellent transitionary structure where you had both more responsibility for your actions and results, and also a forgiving safety net. You’re forced to do near-university-level study of subjects in an environment where the professors are able to hold your hand a bit more, will tolerate late assignments, and if you screw up it won’t permanently tank your future academic prospects.
The tuition at CEGEP was free. You just paid a few fees to the school and the student union, which added up to about $120/semester at the time. This made it a lot more palatable to try out a math- or science-heavy stream and switch out of it if you decided it wasn’t something you’d want to continue in university. The gen ed classes were also great.