There are very few unnecessary jobs in today's economically-rationalised world. Fire the cleaning staff, and see how long your other staff hang around with piling-up garbage and a lack of toilet cleaning/stocking. Fire the receptionists and watch as a ton of work moves elsewhere because you're too hard to get hold of.
That article seems to start with the assumption that the only worthwhile jobs are manufacturing jobs. It's taking a bit of a different slant in context, I think. Above I'm talking about how all jobs in some way enhance the company's bottom line, taking a company-centric approach. The article is talking on a societal level. Corporate lawyers don't help the public much, but they sure as hell help the companies that hire them - it may be a 'bullshit' job, but it's a 'necessary' job (from the fiscal point of view).
Still, I think it's ironic that in one paragraph, dog-washers and pizza deliverers get caned for being bullshit jobs, and two paragraphs later the author bemoans the loss of workers that move things (pizza...) and maintain things (dogs...) :)
Oh, and your customers are gone too because you can no longer deliver any product or added-value. So, no income (except investments).