That's not only a side effect, but a stated principle: After you gain admission, you have to prove that you have the money you need to sustain yourself either through a scholarship, or you have to literally show a bank statement that shows that you have a lump sum in your account that will sustain you for the normal amount of time it takes to finish the degree. Living expenses are factored into this at a set rate. You are not allowed to rely on funds you intend on earning while you're actually studying.
I don't think this is all that wrong: If you are dependent on working to be able to cover your living expenses, it takes time away from your studies, which reduces the likelihood you'll pass, increases the likelihood of needing more time to get to a degree. Needing more time, means having to spend more time with low-paid jobs to sustain yourself until you get to the degree, and it all adds up to a risk that's difficult to manage for the student, and universities definitely don't want the drop-out rate that results from that.
You wouldn't start building a house when it's uncertain that you have enough money to be able to complete the project.
The way to manage the social ramifications is by keeping tution rates low and providing scholarships. Cost of living is not something you can control particularly well although, at Oxbridge, they at least do what they can on that front through university-owned housing etc. Also: Those are university towns that don't have cost of living and rents spiralling out of control as a side-effect of other industries that are there, like is the case in the Bay Area or Boston, which is a major metropolitan area even without the universities.