Illager Patrol Inconsistency

I've been looking through the issues that have been submitted here, and I've noticed that while some players have had an overabundance of Pillagers, I have yet to see a single one. In one persons post, they had a screen-cap of 3 separate pillager patrols all next to one another. Other players have mentioned that they haven't seen any at all (much like myself). What's causing there to be such a disparity of pillagers for the rest of us?