Where I'm from, and this might be universal, those types of firms are either finance or consulting shops.

The actual work practically never warrants the type of people they want to hire, but they pay well enough and they can leverage their prestige. Part of the schpiel is that they can boast to their clients that they hire the best of the best, and thus billing $1000 for a fresh grad is worth it.

There's a lot of focus on signaling. Of course Jane or Joe with a graduate degree in theoretical physics from MIT is going to be able to sift through data and compile spreadsheets and nice powerpoint slides...but it's going to be complete overkill.