I was DI and work with DIs.
On the way back from a meet I once had a conversation with a girl who had developed from a very average All State (small state) HS athlete into a DI All-American. She could not grasp why athletes bothered with DIII.
It made a little more sense to her after I reminded her that in high school and before she moved onto a big college scholarship she too ran for the competition and enjoyment of the sport. Somewhere along the line it became about the money.
DIII is for guys who like to run and can't get a scholarship to do it. I think that is what most people think of the level.
I have always been more curious about athletes who walk on to scholarship level teams...why not go somewhere you can contribute?