Reasons other than "it helps me build a credit history":
* you think you can make more money by investing your 30k and letting it grow and compound
* you are very prudent with your cash on hand and would rather have immediate access to liquid cash than save a little bit on interest which you pay down over the course of <term>
Some of the dynamics here are a bit different when market returns are not looking great/steady and money isn't cheap anymore.