There are countless reasons for doing so. One major one being that people don't/can't drive a massive truck to haul their possessions and would rather leave it

There are countless reasons for doing so. One major one being that people don't/can't drive a massive truck to haul their possessions and would rather leave it in the hands of a professional. Another one being that they're not driving to the place they're moving to, but instead taking a plane/boat/train/foot/bike to get there. Unless they charter private planes or boats, or pilot them on their own, it's a little unfeasible.