The seat someone saves for you is a public statement made before you arrive.

A saved seat is a claim made in public before you get there. Someone declared, in front of others, that you were expected and would be included, and that is a small social risk taken on your behalf. The gesture is generous precisely because it is visible.

Do it more often. Saying someone’s name before they arrive, holding a place, mentioning that they are coming: these establish belonging in advance and cost nothing. And when someone does it for you, it is worth registering as what it is rather than as a matter of convenience, since not everyone is willing to make a public claim about who they are with.