You're Welcome, dammit!

Did I miss the memo?? Can someone tell me when I was supposed to stop saying "You're welcome" and begin saying "No problem?" If I thank someone for something, it sure isn't because they caused me a problem. Saying "Thank you" is a way of expressing gratitude for something someone did for you. Responding that it was not a problem is NOT appropriate!! I doubt I would be thanking someone for a problem!! Could we all try to get back to saying "You're welcome" and stop this stupid "no problem" response?? Thankyouverymuch. (no one better be saying noooo problem!)