This is true everywhere. I’ve been involved polling in for a popular AAA game, a small retail business, school events, online forums, and more; they all fail to account for the “who chooses to answer” bias (is there a name for this?).
I speculate that the “average 4.7 million viewers“ rating Firefly received when it aired was totally off. The Fox executives (who clearly didn’t care for the show, if you read the full story) used this as ammunition to have it cancelled. (see https://en.m.wikipedia.org/wiki/Nielsen_ratings for criticisms of the rating system used at the time).
The people who would take the time to answer a poll (or connect a device to their TV for some cash) are a small subset of people who will skew your data in unintuitive ways. If more business people understood this, our world would be a better place.