What do you mean by 'accepted'. If your R\^2 is low, it's low. How can you not accept it?
I check for normality and typically assume I don't have it.
Yeah, we need to make business decisions. When I worked in academia, there was a tendency (sometimes implicit, sometimes not) to want to find significant or interesting results, so that we could publish a paper, get longer CVs and get raises and promotion. Now we want the truth.
When I'm analyzing an A/B test I don't know what the groups are, I don't know what anyone 'wants', and I'm completely dispassionate. All I care about is getting the 'right' answer. If I ever say "I'm not sure this analysis is appropriate because X" I would be (and am) taken very seriously. (Right now I'm working on detecting differences in rare events - events happen around 0.1% of the time. We have a sample of 1000 (per group). If you have a significant result, I don't believe it.)
That might not be true for everyone.