Overtime the wheel bearings will wear out and the more miles you drive or pull the trailer the more wear and tear happens on the wheel bearing.
On newer cars the wheel bearings are usually a sealed wheel bearing that do not require lubrication but after say 100,000 to 150,000 miles the bearings start to wear out.
When the bearings wear out the debris from the wheel bearings get into the grease and that causes them to eventually go bad and possibly seize up.
If you notice strange noises coming from the wheel area when you speed up the wheel bearings are probably bad and should be replaced.
On trailers or trucks with removable wheel bearings lack of proper lubrication can cause the wheel bearing to fail and then seize up which can cause you to even lose the wheel.
Same goes for the car wheel bearings that are sealed because when they go bad they can too seize and cause the wheel to come off the vehicle which can lead to loss of control of the vehicle.