Moving companies often base their rates on the distance of a move so the point of origin is required.
Just like the Move-from ZIP, moving companies need to know the destination to estimate a cost based on the distance of your move.
Typically, moving companies place a 15% markup in their normal estimates if you are moving during the high volume 'move season' (May 1st - Sept 15th)
Moving companies need to know how much stuff you have. Without a full inventory, most moving companies will assign an average volume per room (~700cu/ft) and multiply that by number of rooms to get an estimate of how big a truck they need.