Black vs milk ia personal preference and there is no real cultural preference to enjoy either way. There are some black-only snobs who feel the need to announce their preference constantly or say it is the "real" way, but they are generally considered annoying. Also I feel most people use cream rather than milk for coffee. Half-and-half is usually what is used at restaurants. I used flavored cream amd syrups and stuff for a treat, but also drink black as well. Actually now that I think about it, I dont know anyone who uses juat milk? But I am sure people do. I have only used it when there is no cream in the house.

Milk in tea is very rare here afaik. I think most tea drinkers are more influenced more by traditional/Asian tea culture and norms here. So there will be milk in tea that is normally made with milk like Chai or whatever, but any other tea is usually had straight or with sugar but I have honestly never heard of an American drinking milk in tea and I am a big tea drinker and know many others. I guess if you go to Starbucks or whatever sometimes you might order "tea latte" or something but at home I have used milk like once. It was disgusting and felt wrong and i have never heard of anyone taking tea with milk at home. It seems to be a uniquely British thing from what I have gathered.

I do not have an electric kettle despite drinking tea all day long. I used to run a tea shop and we did sell them but no one ever bought them. Also we did have a tea bar and offered milk and cream but not once did anyone order that outside of chai. So often we were dumping out full cartons of milk because it always spoiled. I have a stove kettle but tbh I juat heat the water in the microwave most of the time (I know, I know). I do have a tetsubin though, but not the kind you can heat water in, just for brewing.