Eh it's just the language evolving. No problem is synonymous with You're welcome now. I am guilty of saying No Problem a lot or even No Worries.
Here's some insight into it but it's not fact, just a potential explanation:
QUOTE STOLEN FROM INTERNET:
""Speaking of linguistics, there’s one particular linguistic tick that I think clearly separates Baby Boomers from Millennials: how we reply when someone says “thank you.”
You almost never hear a Millennial say “you’re welcome.” At least not when someone thanks them. It just isn’t done. Not because Millenials are ingrates lacking all manners, but because the polite response is “No problem.” Millennials only use “you’re welcome” sarcastically when they haven’t been thanked or when something has been taken from/done to them without their consent. It’s a phrase that’s used to point out someone else’s rudeness. A Millenial would typically be fairly uncomfortable saying “you’re welcome” as an acknowledgement of genuine thanks because the phrase is only ever used disengenuously.
Baby Boomers, however, get really miffed if someone says “no problem” in response to being thanked. From their perspective, saying “no problem” means that whatever they’re thanking someone for was in fact a problem, but the other person did it anyway as a personal favor. To them “You’re welcome” is the standard polite response.
“You’re welcome” means to Millennials what “no problem” means to Baby Boomers, and vice versa.The two phrases have converse meanings to the different age sets. I’m not sure exactly where this line gets drawn, but it’s somewhere in the middle of Gen X. This is a real pain in the ass if you work in customer service because everyone thinks that everyone else is being rude when they’re really being polite in their own language.
Something interesting to note is also the more literal meaning behind these two phrases and how they themselves differ and oppose each other
‘No problem’, coming from a millenials mouth, within the context of helping someone – whether it be holding a door open/picking up something someone may have dropped/ect. – and, naturally, being thanked for it, implies that the kind gesture was indeed, not a problem, that it was just the thing to do, that they were happy to help and that no thanks was really necessary.
While a Baby Boomer’s 'You’re welcome’ in contrast, says something miles different, it actually highlights the fact that the person went out of their way to help someone; almost brings attention to it in a way, saying 'Yeah, I helped you, I did you this favor I accept your thanks.’ which, malicious intent or not, is strikingly different than the millennial downplay of their act of kindness for the sake of helping someone.""
