There was span of a couple years when I had to commute ~3 hours per day. I easily completed 1-2 audiobooks per week.

But more to your point, what percentage of the population do you think is active on goodreads? I can't find any MAU numbers for them, just total membership numbers. Regardless, it is a self-selecting audience. Much like if you go to a theater to see the latest garbage marvel movie, the people in that theater are probably very likely to have seen other marvel movies in the theater recently too.