Sugar kills anything. It also kills the taste of bad tea. So does milk. And lemon. If for whatever reason someone wants to drink bad tea, then the taste has to be obfuscated with sugar, milk, lemon, you name it. (Isn't it easier not to add bad tea to that mix in the first place? I always wonder.)

The taste of good tea needn't be obfuscated. But if one is accustomed to drinking bad tea (which includes all those disgusting sugar/milk/lemon chores), that will manifest itself even with good tea. In fact, that person will not even be able to tell good tea from bad tea.