Shipping huge items takes a lot of time, logistics, coordination and money.
You cannot list a shipment and pay within 24 hours. Lots of times you are comparing prices and there's several other things going on. It makes the shippers planning quite hectic based on what a few of them have told me.
Keep it simple and let the lister and transporter drive the process.
Otherwise, uShip is a great service and I use it all the time.