> The point is that we can allocate this work in a way that minimizes the amount of time everyone has to spend doing undesirable work.
1. Not all work is equally undesirable and the way people are paid is not related to that in any way (in fact isn't usually inversely related)
2. Minimising the undesirable work done in total means some people end up doing almost all of it and some basically none (or, if you consider all work undesirable, some people do only the worst and some only the least bad work).
If before, for example, everyone would spend half an hour of their day to cook for themselves, which might be inconvenient but is overall not a big impact on your quality of life, now we have overworked and underpaid restaurant and related staff doing intense work for crazy hours, which is is a devastating hit to their (and their families') quality of life.
The sum of human effort spent on cooking may have gone down in this example, but instead of everyone being a little annoyed by it, some people are living like kings and some are slaving away for their convenience (obviously this wording is exaggerated, but if we look globally, this is basically what's happening).