How is this different from any other kind of debt a 22 year old might have?
The answer is, it's not - banks simply wouldn't loan outrageous sums of money to 18 year olds. If 18 year olds couldn't get 200k loans from banks, colleges wouldn't charge 50k/semester (unless you think colleges would simply close up shop if they can't charge 50k/year).
Unbankruptable loans + incredibly high demand today means that colleges can simply charge whatever they want.