They do have hotkeys in SC2 and I'm pretty sure you can use the classic ones if you want, but with some of the units changing you'd still have to learn some new ones. And honestly, most of the newer hotkey layouts are more ergonomic. Moving all over the keyboard in the original is a pain. It's nice that they have multiple options now though. If I were starting the game from scratch I'd probably learn the grid layout since it requires the least hand movement.

And StarCraft was about where they really exploded. They were already popular since Warcraft and Warcraft 2 were pretty well known, and the first Diablo came out two years before. Then they had StarCraft followed by Brood War and then Diablo 2 two years later, and Warcraft 3 another two years after that. They were on a hot streak for quite a while there.