Thank you....of course.

I don't go out much, but when I do,  I notice changes.  One ubiquitous change that I have noticed especially from young people is "of course."

In the past, one would say "thank you" and be told "you're welcome" or "my pleasure".  Now the vast majority say "of course."  

I am fascinated by how these verbal viruses are injected and transmitted.  My guess is that it is through movies or television as I do not engage with those.