> "..when I finally pushed for bigger scope at Amazon. My manager’s initial reaction wasn’t excitement. It was something closer to “But you’re doing so well where you are.”", most managers generally push their devs to always be doing larger pieces of work, if they aren't, that's weird.

From the business perspective, it may not be good to push. If they are really good at what they currently do, the manager would need to find a replacement, and there is no certainty that the old worker provides more value in the different job. When only the money is weighted, this will happen often. Seems to fit for Amazon's work culture.

The problem is bored employees find a new job elsewhere. Employees who feel they are not valued find a new job elsewhere. If you can find them a new job in the company you can have them train their replacement - years later the replacement can ask "do you remember why you did...". It also means if the old project has an emergency you have a bunch of people who can jump in much faster - to some extent this adding people to a late project won't make it latter (only some extent, it isn't perfect).

People also get old and retire (or die). By moving people around a bit you ensure that your training plan still works because you are using it. This also means there will be openings to move up the ladder, make sure you get the people on them. (There are stories from my company where after a big layout they got scared and hired almost nobody for the next 20 years, then those who made it passed the layoffs started retiring and there wasn't a mid level of engineers following to promote).

https://en.wikipedia.org/wiki/Peter_principle