Black tea is called black tea because foreigners like to make tea bags and drink black tea (foreigners generally don't drink green tea, saying that all tea is black tea). Unless the black tea bag is taken out within one minute, it will turn dark in a minute or two, and it is really dark brown, so it is normal for foreigners to call it black tea.

Look at this picture, this is the "tea" in the general sense of foreigners.

Foreigners generally drink teabags, not China people. Didn't you say that China people drink coffee and instant coffee, and foreigners grind their own coffee beans? China people pay attention to making tea, while foreigners like simple and brainless tea bags.

The reason is that tea bags and instant coffee are not easy to make mistakes, and the manufacturers have prepared them for you, but they have lost their original flavor.