You might have leaking shower faucet because they are used so much. Leaks are a sign that a part is worn and needs to be replaced. There are many reasons a shower faucet could begin leaking.
Loose nuts. If the leak is around the packing nut area, or at the base of the handle, the nuts might be loose.
Worn out washers.
Poor quality washers.
Improperly installed washers.
Wrong size of the washers.
Disc, cartridge and ball faucets have O-rings that wear out.
Disc faucets leak when the inlet and outlet seals wear.
Disc faucets leak when sediment builds up in the faucet inlet.
Cartridge faucet leak when the O-ring cushioning the cartridge stem wears or breaks.
Inlet seals wear and leak in ball faucet when the O-rings wear out or break.
These causes of a leaking shower faucet are manageable and can be repaired.