> but then we'd need to measure
Most butter here (and in a number of other countries) have measuring lines on the pack itself in 50g increments, so while I agree with you it's a nuisance to have an open one to deal with, the measurement part is usually a matter of using a knife along the marked line...
If the "certain brands" you refer to don't have those measuring lines, though, then a pox on them...
I'm not sure about that, I've resisted buying those brands and it seems poor form to open them in the supermarket just to check.
Do people here not always have an open pack of butter in their fridge?
We have salted butter for the table, and unsalted for baking. We don't bake often enough to want unopened packs if we can avoid it.
For my part: Only around christmas-time, as it's the only time I bake.