No, but a fifteen or twenty minute walk or bike ride can lose out to a free bus. At least some walkers will be enticed onto the bus, which will require more capacity, which will then improve frequency, which will then attract some more walkers, rinse and repeat.

Above a certain frequency buses become extremely unreliable and dwell times start impacting travel time because bus stops only have so much room. With trains you have more room to work with, but once you run out the marginal cost of building new lines runs in the hundreds of millions, if not billions of dollars.