If you were to tell me that I can quit my job and you'll pay me the same amount of money, with benefits, regular raises, etc. all on the condition that I don't do any work, I'd probably become pretty miserable. Turns out, having something to do is pretty underrated, even if the work you're doing isn't exactly what you would choose to be doing. And creating your own work is pretty damned hard.
The question shouldn't be "how do we do away with work ethic" it should be "how can we create a society in which people can still do meaningful work, even when traditional labor has been replaced by machines"