Interesting that they're going this way. We used Google's source repository functionality for a while because there is no real choice if you want to use Google Cloud Builder, which we were testing out for cloud-based Docker builds. GCB was pretty disappointing, and we moved off it. We also found the source repository service annoying. GCB can't pull code from Github, so you first have to set up a Google source repo a…
Having worked for some of the big 5 American tech conglomerates, I would say this is the exact reason why they did not support it initially nor fully. The bigger the company, the more risk their is running/depending on someone else's software SLA/scaling/dependencies/security/privacy/laws... You just had a bad experience with Google cloud but you don't really know if it was google's fault or Githubs.
Plus, they have so many software developers, they can build their own version that conforms to their requirements themselves for practically the same costs.