It's not just you… young agency hires really are culturally different, and in some fairly annoying ways if you're one of the people asked to manage them.
As late as 25 years ago, an unwritten social contract existed between agencies and new hires: you "pay your dues" by doing scut work for unlivable wages, and we'll keep you around for an adequate number of years so that you eventually will be only somewhat underpaid. Starting in the 80s and 90s, the big agencies started to pull back their side of the bargain, instituting layoffs and gutting expensive internal training programs. Leo Burnett was the lone hold-out in spending months to train new media hires before they unleashed them upon clients.
So, in some ways, new hires having an attitude of "what have you done for me lately" might be more appropriate than was the case when now-50-year-old ad execs remember back to when they were new.
Then again, as a Digiday collection of anecdotes shows, it might just be because some of these kids are spoiled. Our favorite: "Only at the agency a few months upon graduation, a young lady walked into my office and told me her dad thought that she was underpaid. I replied that her dad should call me so that we could discuss the matter."