Wow! This is a super strong and a super solid observation. Come to any small bikeshop, and you will find it packed with all kinds of parts - some of which may be laying there forever. But you will most likely come out of the shop with your very specific make and model of bike fixed. Come to a clean and seemingly well-organised and neat bike shop belonging to a corporation, and expect a turnaround time of two weeks to order your specific parts from the producer and ship them. So, indeed, for an ability to rely on the service - be prepared to stock up on things, which you may never ever need.