Student loan interest is mostly not deductible... so older people who buy houses get their mortgage deductions at the expense of younger people who invest in their educations.

Also not deductible: credit card interest, car loan interest for cars not tied to business, personal loan interest... In fact, most forms of consumer debt besides loans to buy houses are not deductible:

http://blogs.wsj.com/totalreturn/2015/02/19/the-loan-interest-you-can-and-cant-deduct-on-your-taxes/