To be fair, unlike google they are not cancelling any services. I think Amazon first builds these services for internal use, and then releases them to the public.
To be fair, you have to pay per unit for these services, so as long as people are using them, Amazon is making money. Putting a service out to pasture in maintenance mode probably wouldn't cost that much.
Maintenance on all of their services is non-trivial in terms of people at least. However if they are used internally, directly or indirectly then they're already paying for it.