Milk in tea is only universal for English/Irish breakfast tea(idk how popular they are outside wester Europe but in England/Ireland if someon says tea they mean breakfast tea and will specify otherwise)for something like chai or eal grey 1/3~(anicdotally) of people who drink it wouldn’t have mik, and the milk isn’t hot it’s normally fridge-cold to room-temp the tea bag is steeped in just water, the point is to sweeten the rea and cool it down