I haven't seen this suggestion before, so just in case people are unaware:
Because Tumblr only allows certain whitelisted sites to be shown in Tumblr's tag searches, linking to itch.io games in posts currently causes that post to become unsearchable.
Patreon, AO3, Etsy, and some other sites have been whitelisted so that they are linkable, but itch.io isn't one of them. This makes it harder to promote games. For example, if I were to post "Kentucky Route Zero is on sale here! (itch.io link)" and tag it with Kentucky Route Zero, if you search Kentucky Route Zero tag on tumblr, the post has a very high change of not showing up. Plus, a lot of fans will include the game link on their fanart because they want to spread the word, only for their art to never show up in the tag and not get seen by people.
Some more detailed posts explaining this:
I've gotten around this with redirect shenanigans, but almost no one knows about this!
A lot of content creators have been calling out Tumblr on this hurting them, but nothing's changed. It would help game devs a lot if someone with more weight could talk to Tumblr and get them to add itch.io!