Re: missing the point
@Professor Clifton Shallot
Mostly for legal and compliance reasons. Back in the good old days each bottle could contain, well, almost anything at almost any %abv. Then along came the Weights & Measures Act which established some conventions (and later amendments) such as spirits are generally sold in fixed sized bottles at a fixed %abv.
Scotch Whisky after distillation and storage typically leaves the cask between 50%abv and 65%abv (although it can be more or less depending on what went in and how it's stored). The vast majority is filtered, blended with other casks (even if from the same distillation) and watered down to 40% to make a consistent product.
The addition of water (even in the factory) releases the oils, esters and aromas, all of which may effect each drinkers palate in a different way, so each individual needs to "add water to suit their taste". Which is one reason you taste the whisky, maybe add a small amount of water, taste and repeat (although if you need to repeat too many times whisky is probably not your drink).
In an ideal world all whisky would be sold "Cask Condition" a la SMWS, but sadly the general public just want their consistent bottle of Famous Grouse or Johnnie Walker.