Here's what a degree is.

You read a bunch of books. You go to lectures. You answer questions to see if you understood the material.

The content is entirely in the public domain. You can read the same content as I did and understand how to build a radio, a bridge, etc, just like me. There are literally no secrets below phd level, and nowadays you even have easy access to multiple explanations of the same ideas.

There isn't even that much teaching, and I say that having attended multiple 2-on-1 tutorials each week for close to 100 weeks. So about 3-400 hours total contact time. Add to that quite a few hours studying for those tutorials, maybe 4 hours for each hour of contact? Depends on how diligent you were.

Compare that to my work, where I've regularly worked 60-80 hour weeks for years and years, of which maybe 40 hours was sitting next to a professional superior. Basically in your first months you spend more time sitting next to an expert than your entire degree. My non-contact hours, where I'd read about finance, was similar: after not very long I'd done a similar amount of non-contact work such as reading a textbook.

My point is that there's no way that university can qualify you for work. Yes, there are jobs that you need specific degrees to get, but even in those jobs you are normally not considered anything but a junior, entry-level person when you finish the course. You're literally not a lawyer when you finish a law degree, and not an engineer when you get your Master of Engineering (like me).

So why do employers want to hire graduates, especially graduates of specific universities and courses?

The reason is they think there's a degree to which people who got into top universities in certain courses are capable of learning the necessary material for a new profession. The material may be completely different from what the person studied, in fact it most often is just so. As what I wrote above explains, it should not take long to cover an equivalent amount of material.

Computer Science may well be the only exception to this rule. On CS courses (I've looked over the shoulder of a couple of students, and I know a professor) people actually do things with a rather large overlap with professional coding. For instance, when I was in uni I built a toy radio and a toy bridge using toy tools. A CS student uses the same Git to version control his stuff, and the same compilers to build them. There's a number of CS labs that maintain actual production code that people use.

This probably means a CS student has a shorter spin-up period, but they still hit the professional time dynamics I mentioned: get a coding job and you'll learn a lot about coding that you didn't learn on the course, really fast.

There are also some economic issues about degrees.

There's a fairly strong adverse signalling effect: if you get a degree but you don't find a job reasonably fast, or you lost your job, why is that? Did other employers interview you and discover some sort of attitude problem? Perhaps I should just interview the regular new grads. You definitely don't know what a professional knows, and I can train up someone smart, and there's plenty of smart kids coming out of uni.

The same goes for your uber driver: if they gave up on getting an actuary job, which is one of the highest paying jobs in society and well worth trying to persevere at, why is that? If he's given up, why would I back him? It's an unfortunate dynamic, but it's definitely there.

Regarding "who you know, not what you know", there's a good explanation for that as well.

If you have a field of people who are "good enough", and you aren't short of them, and they're not easily differentiable, the employer might as well hire his nephew (this is where the term nepotism comes from). And because of the dynamic explained, there's an awfully large field of good enough people: they are mostly a blank slate anyway, having shown just a bit of promise. Of course you'll never know if your nephew was actually among the best, but it will certainly seem that way once he starts gaining experience.

This is why we get a lot of famous peoples' kids breaking into fields like acting, where there's a small number of jobs for a large field of people who could actually do the job. (Though I hesitate to use the same explanation in competitive sports like soccer, where there's a very strong differentiation. Eg Frank Lampard didn't need his uncle to put him on the team, he'd have gotten there anyway.)