A job provides income that pays for the house and the food on the table and clothes for the kids and more. Doesn't matter who tells who to get a job. It's a necessity.

Losing weight is what is truly materialistic, as unless the person that needs to lose weight is morbidly obese and their health is directly at risk if they do not do so, it's something that does not directly affect their ability to get and pay for day-to-day necessities. It's nice if it happens, but it wouldn't directly threaten their ability to shelter their kids, for example.

The two are just not comparable.

If the guy told his wife who did the same thing as this plumber did ($300 in savings at start and no customers for weeks) that he'd leave her if she didn't get even an undesirable job soon, it wouldn't be unreasonable, and would be a more apt comparison to bring up instead of this losing weight nonsense. However, it would be crass for anyone in the relationship to threaten to leave, but you know it happens in a lot of them. :(