Against Productivity

This essay has a lot of good points but seems to be unwilling to bring up the elephants in the room:

Do we need to be productive? If not, should we aim to be productive? What should we do with those who are unable, or choose not to be productive? (Ignoring, of course, the issue of how we quantify productivity...)

Are we not socially useful merely by existing? Is a smile between me and a stranger worthless, merely because it's not 'productive'?