I have a hunch. We were told in marketing research courses in college that humans tend to avoid extremes. If you offer a scale of 1-7, you’ll get a lot of 2s and 6s. My hunch is that media in general, and social media in particular, have changed how people answer surveys.
With the polarization of popular media, bipartisan extremes in politics, 5-star review sites that allow anyone to opine about a restaurant or contractor, and people using the anonymity of Twitter and Facebook to rant and rave like lunatics, I suspect that fewer people shy away from extremes in survey scales.
I can’t prove it, but I bet it’s true. Anyone know a good research expert I can ask?