do you mean that water drips from the opening of the tub spout?
does the spout have a knob you lift to make the shower come on?
if that is the case the water is what is in the line going up to the shower head and will eventually drain out. i usually push the diverter on the spout down after a shower and it drains out right away. the water that is still in the shower head may drip out after a shower also. if it isn't dripping all the time it doesn't sound like a problem.