The type you get might not really be butter. Or you might keep your fridge too warm.
I've found that butter flavored spreads stay soft in the fridge, they are usually a mixture of artificial fats and oils and aren't really butter. (e.g. I can't believe it's not butter)
I've found that...
Usually we keep unopened boxes of butter in the freezer until needed.
We keep the stick we are currently using on a plate on the counter. And we keep the rest of the sticks from the box in fridge.