Well, Uber drivers definitely directly support Uber's primary business. So I'd say that's a different situation altogether. (and they're not really outsourced, Uber directly "contracts" each one of them) Many businesses fail when trying to outsource staff that directly support their primary product or service.
A more direct comparison to the issue of Frito-Lay's janitorial staff is something like: should Yellow Cab should hire their own car wash staff or make a deal with a local car wash?
Yes, the decisions could go either way depending on circumstances. I think for me this was a good example of needing to stay on topic. Original comment was that not paying a middleman is one potential benefit of keeping common services in house and that many if not most roles could be filled externally.
A more direct comparison to the issue of Frito-Lay's janitorial staff is something like: should Yellow Cab should hire their own car wash staff or make a deal with a local car wash?