Innertube producers probably produce different grades of tubes, as well, so that they can offer different price points. I don't know that's true, but it would be the rare industry that doesn't do something like that. Rubber producers, like Exxon, sell different grades of butyl, which I imagine result in tubes with different characteristics, or maybe old machinery that hasn't been updated is still used by some, resulting in finished products inferior to modern standards. Certainly somewhere in the production chain, there are differences that affect quality.

Whatever the precise case may be, there's little doubt in my mind that tube manufacturers are making compromises with regards to quality, cost, and value. Except in the cases where, like Michelin or Schwalbe, the manufacturers brand name itself has market value, there's probably little incentive to manufacturer the best tube possible. If you can land the Giant contract, so long as you're not having x% of tubes fail during assembly, you're golden. Other than that scenario, I wonder if there's any feedback loop at all?