Why do we need to work?

I’ve been reading David Graeber’s “Bullshit Jobs” which I got into after reading his essay on it a few years ago (here). At the time I was struck by the comments from Keynes (Economic Possibilities for our Grandchildren – here), who believed that in 100 years, technological developments will be such that all activities will be conducted by machine’s and so humans would only choose to work around 3 hours a day. Keynes believed that people would still choose to work a little amount – witnessed by the fact that at the time, the wives of the very rich, often spent some time doing charitable work – so that we have a sense of purpose and because some jobs are enjoyable. [...]