That's pretty common actually. It's called IWB CC (Inside Waist Band Concealed Carry). There's also AIWB (Appendix Inside Waistband), sometimes just called Appendix carry. The big issue is that it's not inside a holster. The holster gaurds the trigger so that an ND is more difficult. Holsters also have retention so you're less likely to have a gun drop, where the gun falls off your person unexpectedly.
Came to comments to say the same thing. Had a friend put a bullet through his thigh. The bullet was stopped by his knee-cap. He had his 9mm tucked in his belt. He was hiking and stumbled in rough terrain in the middle of nowhere. It was tucked more to his side, so at least his dick wasn't at risk....he said the helicopter ride was fun though!