Well, just to cite one factor, it might work better under conditions where we aren't literally putting people's lives at risk by asking them to shop instead of us shopping for ourselves.

In other words, conditions in which the pool of labor is less heinously and obviously exploited and better workers are easier to recruit for the job in question.

While I agree with you about that, I don't think most people have that logic when they consider ordering on insta-cart. If demand for insta-cart is dropping I would wager that doesn't bode well for its use in the future regardless of the level of talent/exploitation of the employees.

In other words, if all of a sudden insta-cart was much more generous with their employees and managed to hire better talent, that wouldn't likely translate into more demand for their product. Yes places like Trader Joes treat their workers well (and build brand around that) - the lions share of demand revolves around on merits/price. I wish it was more along your factor but sense that it isn't a factor with an order of magnitude change associated with it.