Mine only gets a bath when he goes to be clipped (3/4 times ayear) or when he has rolled in something exceptionally smelly! I prefer to brush him - when he lets me!- so it doesn't interfere with his coat and the oils in it as he does like the water!
Depends on the dog , and how mucky it gets !!
My two deerhounds get a bath if they have been out in any gross mud or rolling in the remians if dead hedgehogs/ birds/ rabbits etc etc !!
One of mine goes to Hydrotherpy every week, but they only get properly bathed when needed. I haven't bathed mine for several months. I do them when they stink/been rolling in dead things, or the coat has become dull and a brush just doesn't cut it.