Even without considering laptops, I can already imagine quite a few circumstances where someone might want monitors of differing DPIs. I’ve actually thought sometimes of getting a smaller monitor I can have off to the side that I display a browser window containing mostly text on when I’m playing videogames or working in something like Blender or Aseprite; yknow, for referencing a guide, wiki, or manual or something. I don’t even have a super high desire for a multi-monitor setup outside of that.