why do people act like concert encores are still a surprise

theyre so obviously planned at this point. like yeah the band leaves the stage for 2 minutes and then comes back to play the 3 most popular songs they didnt already play. its not spontaneous its just tradition i guess i get why its done but pretending its some big unexpected moment feels so weird. kind of like how coffee shops always ask if you want room for cream when you already said black. youre just going through the motions. its not even a bad thing but still