Milk sugar in your stout is like cream in your coffee.
Sweet stouts, also referred to as cream stouts, have less roasted bitter flavor and a full-bodied mouthfeel. the style can be given more body with milk sugar (lactose) before bottling. malt sweetness, chocolate, and caramel flavor should dominate the flavor profile and contribute to the aroma. hops should balance and suppress some of the sweetness without contributing apparent flavor or aroma. the overall impression should be sweet and full-bodied.
The number one reason is craft beer tastes better than the "beer water" that is mass produced and mass marketed by the big beer companies. Craft beer tastes better because craft brewers spend their time focusing the quality of their beer rather than focusing on their marketing campaigns and stock prices.
Oh yeah! Craft beers can pack a punch. Most craft beers range from 5-10% ABV, but some can reach 20%, 30%, and even 40% ABV.