I don't think its just the "prestigiousness", I think its also the job security and flexibility. Trades are a great way to make good money fast when you are young, but if your body fails early or you get older then trades are often really hard to pivot from. And if you get injured at any point (very possible) then you are often SOL. I work in social services and the number of former trades people who used to make 6 figures who come into my office living on welfare is alarming. Our social safety net really fails trades people.
In addition, the requirements to get into trade school have increased. There are tons of newcomer kids who want to get into trades, but the industry and the schooling is not accessible to them. I once sat in a presentation from "Careers: The Next Generation", who do alot of the Registered Apprentice Program in high schools, where they bragged about only accepting kids with good grades, impeccable attendance, and perfect English. If you are smart enough to get into trade school then you are smart enough to go to Uni, why would you pick trades?