i dont understand why a company keeps the last check after a person quits.

You mean keep the last check? Or hold back the last check ? Unfortunately some drivers feel the need to trash the truck or abandon it when quiting, but they probably forgot or didn't realize that they signed something in orientation stating that the company would withhold their last check to cover expenses or something to that effect. 8)

i told my dad if he wants to quit try quitting the right way and he might keep his money