The explanation for BS jobs is that the economy is not nearly as "efficient" as we hope that it may be. Incumbents at the top, stay at the top, regardless of how inefficient they may become. A number of forces including government and regulation, and barriers to entry confound to reinforce the position of mega incumbents that simply stay at the top forever.

On the plus side, I'm hopeful that the rise of BS jobs will increase work life balance.