The reason they can get away with this is because your data is already at AWS. It's a lot easier to use a new service if the data you need is already there.
That's their advantage. That's where the real lock in comes from. Not from you using their services, but from you keeping your data there.
They win when the first comment in any technical-requirements-finding session is "well AWS has <X>... that could work?".
New companies choose AWS almost by default these days, and the alphabet soup of services available means that it's got an answer for just about any paradigm you're interested in, which means there's no reason to leave.
The proliferation of half-baked services at AWS will never end. They won't become fully baked either, because that doesn't make business sense -- doing just enough to capture new business is most efficient, and in the worst case just let some partner build on your platform and offer their services.
But I agree, too much stuff under the AWS umbrella, and trivial ones like this, will impact the brand image.