at the end of the day, if they can offer you it at that price whilst still being able to maintain a physical premises, staff to help you and look after you after you walk out of the shop then they will - simple as that.
An online store needs a warehouse, computer system and a couple of guys to pick and arrange couriers to deliver items to you (alright there may be more but you get the idea) they don't need to know anything about what they are selling or how to set instruments up. They could pay a guy to sit at home and answer techie questions by email.
I'm happy buying online as I generally do my homework but more recently I prefer the situation where I can call the person I am buying my gear from and get it delivered, still sight unseen and slightly more expensive, than just pressing a button and hoping for the best as I know I can pick up the phone if there's a problem.