I don't think Github are looking to implement the whole CI process.
They want to host code and integrate neatly with other CI providers.
I think that makes much more sense (why abandon Travis or Heroku for the sake of having "one" platform to rule them all... ?)
Using both regularly, the whole create issue 1234-> autocreate branch+MR -> git fetch+checkout 1234<TAB> -> code -> git push -> review -> resolve discussions+open issues for unresolved -> merge+autoclose+autoremove branch -> git fetch --prune flow is downright awesome† and really acted as a catalyst. GitHub just feels so antiquated and cranky compared to that so depending on what you're looking for this frustration can definitely go both ways.
† and it'll be even more awesome when we will soon enable per-branch review deployments which get auto-destroyed on branch removal, followed by auto-deploy of master in staging + manual in production, all neatly tracked in the environments tab.