I think the larger reason being an "AWS expert" is a job description is lock in. If you've hired people who have spent years grokking the AWS names, terminology, and options then your likelihood of switching to anything else is much lower.

Not that AWS doesn't also enable scaling or something, it just (conveniently) doesn't give an option to deploy anything but scalable services you'll train your staff on. A lot of the time AWS interfaces/offerings are copied not because they were ideal, but because it's an easier way to break past that barrier with your offering.