Why do people borrow on DeFi lending platforms?

I noticed that most lending platforms will ask you to deposit a collateral that is at the very least equal 1:1, if not higher than the loan amount.

Its fairly standard practice for protocols to limit a user's borrowing option to 75% of their collateral.

Why would anyone seek to borrow crypto by locking another one as collateral when they could simply trade one for another on an exchange, and at much lower rates than the massive rates we see on DeFi lending platforms?