that is why you have a person on front of store, in saying that though I have been in shops where I have been greeted by a few different staff members, I don't leave thinking how bad they are, I always feel great that they were so friendly, there is a line where it can become pushy if you just ask if you can help, but if you greet someone with a hello and a smile they will usually be more inclined to ask for help because it makes them more comfortable.
one of the parts to my position is finding good staff, I am always on the look out for someone special, I can tell you if someone doesn't greet me when I enter a store they wouldn't get a second look.
Check out stores like Bunnings and Mitre 10, very competitive market and always someone on the door greeting all customers.