It can be, they just chose not to (with ulterior motives or not, I cannot say.)
For my side project, I am using a dual-licensed MIT/Apache (your choice) but with an exclusion which prohibits companies like AWS from offering it alone as a service. Here's a copy of the (quite human-readable) license:
https://gist.github.com/slimsag/2164520b9e249fbae4e08e2bdf6e...