Other commenters have covered the organizational inefficiencies that allow bullshit jobs to exist pretty well. I'd like to also point out that larger organizations have more of these inefficiencies (part of what is known as "diseconomies of scale", the counterpart to the more well-known term "economies of scale"). Our capitalist society actively subsidizes larger organizations, both literally and figuratively, resulting in more bullshit jobs and more economically wasteful behavior in general.

A non-capitalist free market society (such as a mutualist one) would have significantly smaller and more efficient organizations across the board. One can't eliminate organizational efficiency entirely, but we currently have a lot of room for improvement.