paddyann It already IS the norm! 
I like when going into a shop if the person greets me and then just says something like, Let me know if you need any help.
I also worked with the public on the other side of a till in a high street grocer for a short while. Customers came in all varieties. Pleasant for the most part, some chin-waggers (held up the queue!), several grumps, etc. Someone actually complained that I did not hand her the coin change properly!
But the 'worst' was an older lady who bought a bottle of vodka every day without fail, smelled awful from the urine stains on her trousers, along with unwashed body and hair, but had a glorious smile and always wished us a nice day. After she left, staff would rush over to the till area and spray bathroom scent to cover up the stench. It was heart-breaking. 