We do have platform-specific filters, but I can think of two usecases off the top of my head where icons on the game tiles would be handy:

Use Case 1: Installed games

The installed games filter is supposed to show you all games installed on your machine. Say you have two copies of KOTOR 2 installed, the GOG version and the Steam version that's bundled with TSLRCM. Which is which?

Why would you have two of the same game installed? Perhaps you modded one game, and kept the other pristine. Or you're running different versions (Say, latest beta Stellaris through steam and the stable from GOG).

Or, the case may be that you have duplicate games you want to uninstall.

Use Case 2: picking the right game to install

Say you have a game that's been on multiple giveaways/bundled. Say perhaps you own Mutant Year Zero on GOG, Steam, and EGS (I don't on GOG, but I do on the other two). Say you are browsing the "All games" page to see which games you have, and which you want to play. Say you are not using the platform filters for a reason, because then you'd see the same game perhaps 3 times while viewing different filters, and install three copies of the same game (see Use Case 1 above).

There are reasons to have platform icons on the tile screen.