>Has anyone else noticed that "You're welcome" has been supplanted by "No problem"? You say thank you and they say no problem. When and why did this happen?

When Ahnold said "No problemo" in one of the Terminator movies?????

Language evolves. Consider how English has been de-sexed over the past couple of decades with, for example, nouns ending in "man" be replaced with something gender-neutral or the use of "their" as a singular possessive meaning "his or hers."

I haven't looked for them, but I'm assuming dozens/hundreds/thousands of studies have been made showing how English has changed over the last (pick a number) years.