'Ethical concerns' only covers a subset of these cases and the phenomenon is noticeably similar across the entire set, so I don't think ethics is a convincing explanation.

People reach for the handiest hammer, but it doesn't follow that the hammer is driving the hammering. Ethical concerns are the best hammer, of course, because then one's own motives are unimpeachable; but failing that, you'll see comments about the business being shitty for other reasons—"it used to be good but they've been declining for years and I can't even use it anymore" is one, and "how is this a viable business, look at those financials, doesn't anybody care about profit anymore god this world is insane" is another.

I don't believe Dropbox threads are generally friendly to Dropbox anymore, and I'm pretty sure Digital Ocean has been on the rack here too. Today's thread was a noticeable exception. Most S-1 threads are pretty cranky in general.