>I doubt a customer asked AWS: hey, can I get a graph of how the resources in my accounts all interconnect while maintaining the clusters for the data stores, handling upgrade, security, etc. myself and paying hundreds of dollars a month for the pleasure?

I do consulting for a company that works with a lot of AWS customers and I think you'd be surprised. They don't put it in those exact terms, of course, but I have personal experience with a customer who specifically did want (I think due to their own internal regulatory standards) to maintain their own data stores rather than having an AWS managed service. In my example, it was using AWS Config versus having their own in-house software built on top of Lambda and RDS that did the same thing.

Another situation I've seen a lot is that really large companies have a tendency to think they are a super special snowflake with special use cases that no AWS-built service would ever fulfill, and thus they suffer from "not invented here syndrome". I've consulted many companies where I pitched them using an off-the-shelf product or service, but they will insist that it only covers 90% of their use cases and instead they will build their own custom solution using the AWS core services as building blocks, resulting in something similar to what is seen in the OP.

For the record, I think it's dumb as hell in most cases and I'm not in any way advocating that this solution in the OP is preferable in any way... but unfortunately I do understand how/why it was probably created.