If Safari didn’t aggressively cache favicons, websites trying to overcome Apple’s objection would immediately start trying to use window.reload() and server-side dynamically generating favicon paths, for random “I made this up before coffee” example, which would burn more battery power on Apple devices for endless page reload events. Caching aggressively makes it a non-starter to try and engineer workarounds, and comes at zero impact to users (who are either accustomed to the old favicon and don’t care about rebranding, or ignoring it).