Sure, you sound like anyone can just have a eureka moment and come up with an algorithm. Uber has a legitimate use-case that fits their needs on ML, so they build it for that need. And why not just also talk about it too as a lesson-learned for others.
Do you simply have very high expectation of everything in this world?
There are plenty of meaningful ways to contribute to the body of open source software that don't require strokes of genius. Bug fixes and refactoring come to mind.
I just picked this thread as a starting point Uber may have a legit need for a particular framework.
My main point is there is no need to make frameworks for frameworking's sake. Purposeful OSS collaboration is just as good, if not a better way to gain influence than a PR splash.
Of course that assumes that the goal is to make cool things, which seems loosely connect with wooing investors at best. (Again in general, not picking on Uber.)
I don't work in Uber's team on ML, so I can't answer this, but I also cannot just simply assume everything is built-for-PR-splash. You can argue why can't they simply talk about the reason of not reusing any existing OSS framework than building yourself, but making an assumption that they did it for the sake of PR is lack of factual support. Are we now living in a world assuming everything Uber did was for PR? Last I heard they had 1500+ engineers and with that size, I am sure they can just talk about things they have done in the last few years.
Do you simply have very high expectation of everything in this world?