As other comments have noted, avid readers raise the mean considerably.
Which is exactly why any reasonable person would look at the median rather than the mean. I also think you are greatly overestimating how many avid readers there are. If one in ten people reads a book every month (which seems very unlikely), that still only amounts to 1.2 books/year on average from them.
Why? This is not some great divide where 50%+1 read no books and 50%-1 read a book per week. If you want interesting information with details you’ll look at distributions and historical trends and so on but if you are only looking at 1 or 2 numbers, you’ll get limited info.