Then you can find that game page more easily next time, if you want to play it again (or if you want to check for updates, or give feedback).
You can also create public collections, to show your followers and possibly others what the good games here are (I have three such collections, you can find them on my creator page).
itch.io (most likely) also uses collections to determine the games that should be at the top of their recommendation lists, or on the front page, but the details behind their recommendation system are a secret (for a good reason).