I can honestly say that before moving to Japan I have never bowed. I cannot think of a single instance where I bowed.
Now, I do it frequently without thinking. An odd transition. Why do it? Because it is common and you get used to it. It is also quite polite and fits perfectly in this ordered society.
Although they do take it to the extreme sometimes which make me smile. The other night I had to pick up our car from the shop after a few minor repairs.
The bowing included: the owner of the shop bowing as I drove away, one mechanic who started the car bowing as he let me in the car, one mechanic bowing as he stopped traffic to let me out of the parking lot and the last mechanic standing by the doors of the garage bowing and saying Arigato.
You don’t see that kind of service anywhere else.