a) We spend money marking and signing cycle lanes on pavements. It would be better to allow cycling on all pavements except in areas where expressly prohibited (e.g. busy city centres, pedestrian areas).
b) Better for the enviroment, more people will cycle when they feel safer and don't have to be on the road.
c) safer for cyclist (less risk of being hit by car), safer for motorist (reduced need for overtaking)