If invisibility would always be in effect it would simply be a +sneak modifier. Now, because that it breaks when you interact, it changes the behavior a little bit by allowing you the first half of a successful sneak but still makes the escape a dangerous (and thus fun) experience.
I get what you're saying though, picking flowers in the wild and breaking the spell seems a bit excessive. But I don't agree that it should always stay on even when you attack someone. Locks ok, pick-pocketing maybe.
Easy to mod I guess.
yeah i understand what you're saying, i wish it would last more than 30 seconds
Dual cast it. I think it becomes 66 or 99 seconds (Not sure atm, 66 makes more sense but I recall something lasting 99 seconds)