I have a older style bladder tank that is about 6ft tall. Pressure gauge always reads 40psi, it never gets above or below 40psi. The pressure switch never kicks on or off because the pressure never drops. Pressure in house is good excepts every so often there is lots of air in hot water line.
Option 1: the well is uphill (about 92 feet vertically) and a pump is entirely optional.
Option 2: the well is textbook artesian, (water comes out the top under pressure equivalent to being 92 feet uphill, unless a pressure seal is in place) and a pump is entirely optional.
Option 3: the pump is running all the time, and is worn out, and can't make enough pressure now to ever turn the pressure switch off. Can't be doing your power bill any good.
Option 3a: There's a leak in the pipe from the pump to the house. If the pump is submersible and the leak is in the part of the pipe inside the well, you would not see a wet spot, but you'd be pumping water in circles. If the leak is the right size, it might be holding your pump from ever getting above 40 PSI (But I consider worn out pump more likely, usually.)
Option 4: the pressure gauge is broken and stuck at 40, but "pressure in house is good" trends away from that.