Why don't Plex cache the movie posters at the client.

when I scroll in my android app and in my desktop client the posters are always blank whenever I start plex and when I scroll down it downloads the posters as they get reveled in the client. and even more annoyingly, If I scroll back to posters that I just viewed they are gone again and I’ll have to wait again for the re download to complete. why don’t plex cache the posters ahead of the scrolling and keep all the posters that it have already downloaded. ideally, plex should cache all the movie posters so scrolling isn’t such an annoyance but I’d be fine with it caching posters downloaded this session.