I came across an article recently that talked about how while 'please' and 'thank you' are still in general use 'you're welcome' is getting rare, and have noticed this myself - it's very common to see an exchange like the following:
Cashier: ...and, thank you for shopping at ____. ::hands over grocery bags:
Customer: No, thank you.
So, I started to think about what this shift means, and whether it's really a bad thing. Often, it seems to be used to show an egalitarian mindset. A cashier or other service person may be grateful for our business, but it's as valid to say we ought to be grateful to them for the service/help they've provided. That perspective, if genuine, I can't condemn. 'Thank You' - 'You're Welcome' still has a place when there is a clear receiver and giver of some boon (such as a gift or an excellent letter of recommendation) but I think we may be right to reconsider the old script in other situations.