> I'm convinced that most office work exists for social reasons

The powers that be are not competent/powerful enough to engineer a society-wide conspiracy like that.

A lot of waste (especially in big organizations, and the bigger the organization the more capacity for waste) happens, and the more the income is detached from production (e.g. governments get tax revenue regardless of how well they spend it) the less people care about efficiency.

But for the most part people get hired because somebody thought that makes business sense to do so.