My well driller says I need a new well. Why can't they drill my existing well deeper?

When they drill a well it is either pounded in or they drill a bigger hole and insert the pipe with a expanding filler that seals the pipe tight so they can't. If they do it will cost more than drilling in a new spot.

Because sometimes wells fail after a number of years and need to be relocated, since you can't really be digging in the same spot :)

With as much as it costs to drill a new well, I would definitely get a few more bids.

A few reasons may exist. Maybe the water table you were hitting has dried up and a new location is needed. Another reason may be as simple as drilling a new well costs more for you and means more money for them.