Why care about upstream?

They dislike being called on it because it's the truth. It's rather well accepted psychology that no one likes to have their hypocrisy publicized and commented on and will react very negatively when it does occur. Shuttleworth/Canonical/Ubuntu have engaged in numerous public events where they lauded the Ubuntu approach and either chastised the community or made suggestions on cooperation (depending on your point of view mostly) then proceeded down the same path the community has been criticizing them on for 5 years or more of near zero upstream cooperation.

Let's be honest people, we've been talking about Ubuntu needing to move more stuff upstream for a VERY long time and little to no progress has been made on that front. The community gave him multiple years to get things going before serious criticism even started. Shuttleworth talks a good game and I'll even admit they make good suggestions from time to time and do some very good things, but he runs his business like he's in the standard proprietary software business. Copyright assignment, keeping key components proprietary and closed source, throw it over the wall open source and numerous other actions that do little to advance free software. The worst thing about it is the community has been discussing all this bad behavior for several years and very little has changed. I came to the conclusion about a year ago that nothing will ever change and as a result Ubuntu will die eventually.

RedHat's success (even SUSE to a lesser degree) has a lot to do with their complete commitment to open source, their prioritizing of upstreaming everything possible and taking valid criticism and making changes. I can remember a lot of mistakes Redhat made over the years (bluecurve has been mentioned but there have been dozens of incidents) but rather than continuing the same policies they take the criticism seriously for the most part and adapt their policies. Shuttleworth/Canonical seem to approach everything as if it's their choice and nothing else or anyone else's opinion matter. For all his talk he still apparently doesn't get FOSS and for that reason alone I don't see Ubuntu as a long term success. Once Shuttleworth cuts off his private funding it's a dead company and a lot of that has to do with their policies IMO.