I find this useful when social network services like Mastodon, PixelFed, Nostr, and Bluesky all have multiple client apps and many have pretty obscure names. I want to quickly click on, say Nostr or Bluesky, so I have changed the icons and names for the apps that I use for these services.
But just for icons sometimes you want to see icons that match the rest of your home screen, so there are quite a few reasons why you may want to do this.
Icon packs allow you to change all the icons to match a particular different theme you want to use.
See https://www.androidpolice.com/how-to-change-app-icons-on-android/