But they wouldn't feel that way working just anywhere. They have found a great match with an employer who treats them well.
Although, I don't think work is the default for humans. Evolutionally speaking I'd think taking care of the self, the partner, and the immediate next of kin would come first, and would take most of the day. In this light, a 9-5 is really unnatural, because you give "your best" to a completely different context. I see the point in it personally, but I also understand why it could feel unnatural and undesirable.
Things can be both enjoyable and necessary[0]. I could imagine that early humans may have enjoyed the "work" of hunting (given that some modern people still seem to), even though it was also necessary for feeding themselves.
[0]: Money being a stand-in for "necessities" here.
I've learned that this sentiment is somewhat uncommon, though.
Just look at nurses. They are chronically underpaid, yet still do their jobs.