Because for whatever reason, the developers never considered the possibility you'd get stuck with useless cards. (gamingreinvented.com)
So once you're out of useless cards and running for the hills, you now get to watch your entire deck go straight down the plughole for good measure. (gamingreinvented.com)
Those cards in particular are prone to hate - drafting (i.e. drafting nearly useless cards that you see as being highly valuable to the game's leader). (zenofdesign.com)