Honestly, and speaking from someone who has experienced what you're describing? (I'm aware it's bad don't @ me I'm working on it lol)

It's coming from a place of envy. I would love to be able to read that much in a year. Unfortunately, my job and other responsibilities just don't allow for that time, period. I'm sure other people have a similar sentiment of a knee-jerk "well they must not work/do anything worthwhile with their time" sentiment. Throw depressive episodes in the mix and oh boy do my hobbies suffer. To no fault of anyone but my own, I do realize. But I suspect that it's a common mentality for people who are hating on the 100+ readers.