Me, I don't often change my profile picture, regardless of the website I'm on. I only change it when I put a random profile photo just enough time to register in order to put the "official" profile photo, therefore more legitimate. Since I started to be an actor-user of the web and not a visitor, reading lots of articles and looking around, I came to understand that I had to adopt the same identity everywhere. Almost for the same reason as underlined @gmaximin
Otherwise, my profile picture is fairly recent. I started using it on another comic book sharing website. And to a report with a comic book project on content creators:

This drawing was made with the drawing mode of the notepad application on my smartphone.