We may have unlimited resources right now, but i would not call it “creative mode.” I think the current break timers are serving two purposes right now.
1) I think they are the base break timers for survival mode. In later updates, you will likely be able to craft faster picks.
2) The long break times help discourage griefers from destroying massive areas.
That’s pure speculation, but I doubt the devs will reduce break timers till they introduce faster tools. I do agree that carving out mountain sides is painfully slow. I’d suggest you find a cave system to work in :/