brakes bite harder at first

I was wondering why do most cars that I have been in (mostly honda's) have a much better brake bite and grip than after driving it for a while, like when i first start the car and pull out, the brakes seem to be working much better than after the car has warmed up and such.... anyone know why is that? i've noticed it on a few cars, not just one so i dont think its a specific car issue...