There are lots of pragmatic reasons you might want to work at Amazon for a while and then leave for example, someone who's studying and wants to move into some other line of work after graduation. Waiting tables is the stereotypical student support job (partly because of lectures during the day and people preferring to attend restaurants in the evening), but my understanding is that Amazon warehouses run more or less 24-7.

Another way to look at this that doesn't require any cognitive dissonance is that Amazon lets hourly employees accumulate up to 2-3 months of severance pay (I'm not sure how much time that represents because I don't know their hourly rates, but I'm guessing it averages out to something like $12/hour).

I think it's a great program. Besides offering a friendly incentive for unmotivated workers to leave; it improves the confidence of those working there and provides useful transitional assistance to those moving on for career reasons; lower-paid workers often suffer economic disruption even when moving to a better job because they may miss a pay cycle or have to take on new expenses (new work equipment, different clothes, a car or moving to another town), so a cash cushion for such things is a big plus. It's good cheap publicity for Amazon, not to mention they probably retain their ex-employees and their associates as future customers.