how long until the phrase, "you're welcome," has disappeared entirely from the wider lexicon? it cannot be far off.
i do wonder how the trend started; my guess is over-eager employees sucking up to management or to customers (possibly by direction). if i'm the employee and you're the customer/boss, i hand you your purchase/report(?), at which point you say, thanks. if i say, you're welcome, then in some small way you are in my debt. rather than put it in your mind that i've done you a favor i must make you feel indispensable in this transaction and respond with a thank you on top of yours.
instead of responding to what you said like a person well-versed in conversational language, or an even semi-well-programmed machine, i'm just going to trump your thanks and force you to continue the conversation by saying you're welcome for coming to my store/giving me a job, weird, or maybe go nuclear with a third consecutive thanks. the only other alternative, and the one most often applied in my experience, is to walk away from the second thanks almost as if it was never uttered, which to be fair it shouldn't have been.
i've actually had discussions where i defended my position that i am pro-language mutation over time as opposed to static norms, but only when they make sense and this one doesn't. you know how in some languages the same word is used where idiomatically we would say please and you're welcome? i am assuming there will soon come a point where we use one word for all three, it will be thanks and it will make no sense at all for the people who didn't grow up with it. and that is how old people get so confused. i didn't see this conclusion coming.