I've no idea what you mean by the second part but the first part is a falsehood because the fact remains you and I already are already paying to train the next generation of merchant bankers and stock brokers. They just "promise" to pay the money back but they'll already do that from the sums of money they earn in fact in terms of tax they'll put far more back into the system than you or I probably will in our lifetimes.
Now here's another part that gets my goat a little about the entire situation if you do your degree in a subject area that does not pay well (under 21K in current rules) and you never earn above that threshold after 30 years we just write off the debt meaning that johnny taxpayer did pay for your tuition. Now obviously there is some sensible reasoning behind that but take a degree that leads to a way paying job and you'll have to pay additional tax for probably most of those 30 years. Now I'm actually lucky my student loans amounted to just under half the current values so I will pay them off long before 30 years mainly due to I was in the first batch of students to have to pay them but now you have to earn ludicrous amount. Some very quick maths a three year course outside of London will incur debs of 37,500 that means to pay it back over 30 years with the 3% interest means you need to pay back £158.10 per month. Under the rules for paying it back that means you have to earn £42,080 every year (obviously this varies as it's 9% of everything you earn over 21,000). Just as a hint I don't earn close to that much in a well paying job (software engineering) 8 years after finishing university so even my debt will likely be written off under the current loans.
Another issue is in my current financial situation I could really do with the money I pay back in my student loan. My wife and myself are saving to get a deposit to buy a house and are trying to start a family with the reduced hours she'll be on things will be even tighter. In 22 years time I should be way better off in theory but that's the point the government decides I no longer have to pay the money (like I said though my loans are far less than current students so it's not completely true as I'll have paid it off before then).
Part of the reality is we are paying for fair amount of tuition fees we just try to convince ourselves the students are. The system is just massively unfair on some students and not to others as J'nuh alluded to if you earn mega bucks you can probably afford to py it off early so get more of your money earlier.