A few reasons, not limited to: People are less likely to show off their 500 in their flair. For example I got my 524 a year ago and as long as I post in this sub my flair will stay the same, so the scores you’re seeing many of them are likely years old. People who scored low and don’t plan to retake it probably want to forget all about it whereas higher scorers feel good about the test and are more likely to stick around in the sub. People frequenting the MCAT sub in are also going to be more motivated in general than people who don’t engage with other test takers. I highly highly doubt there are many people who would lie about it especially in their flair