I only tap mine if there's a reed sticking.
The main drawbacks to harmonica playing are facial hair (ow! that hurts!) and the small bits of detritus that get stuck in the reed and then release quickly on a suck note, hitting the back of your throat with extreme velocity.
While the gob iron players are here, might I extoll the virtues of the 'low F' harmonica. F is a good singing key and the normal F is a bit squeaky. Get a low F, they're wonderful, especailly those clever valved ones. And you don't get your hair stuck in them either.
Keep on sucking