How you boil the water is meaningless so long as you take steps to ensure the water has had time to even out its temperature across the container. In my view, it is how you actually brew the tea that strongly influences the aroma and taste of the resulting beverage.
Additionally, as Hedgie points out, people develop strong preferences to certain methods and certain outcomes. Sometimes these are hereditary traditions, handed down from mother to daughter for generations and take on the form of identifiers of your social acceptability. Indeed, deviating from these assumed 'norms' are a cause of horror completely out of proportion to their actual effect on the drinking experience.
A good example: When making a bag-in-the-cup picnic tea, when does one put in the milk (for English tea is commonly diluted by a small amount, say about 50-100ml, of milk)? To me, putting the teabag in with the milk is ridiculous as it will completely change how the brewed tea tastes; yet, to my mother, not putting milk into the cup before the tea (a reflexive pattern that assumes you brew the tea in a separate pot - either with bags tea in a strainer) is unthinkable and, indeed, a gross social indiscretion as well as a cause for personal shame. We have had quite serious public arguments about it.