I can understand new players playing standard as they have really only played the one class tutorial and unlocked the core set so standard would be the way to go and only playing 1 class makes sense as that would be the only cards of value they would have unlocked so far (fire blast/ flamestrike/ etc). But eventually you buy packs with gold or get them from tavern brawl. you wont be getting only the one class of cards so you;d save them all until you had enough for a 2nd deck from a different class you;d been playing, rinse repeat.
Going single class and using the core set and dusting anything not those 2 sounds like the worst way to play. If thats how they enjoy it so be it… I cant imagine playing the same class or really the same deck more than twice in a row.
just boggles my mind how limiting some people make the game for themselves.