It doesn't make sense to "delete" campaigns in the traditional sense. How would you then get stats on your total spend over time, etc. Those stats are needed, and to remove them would cause even more confusion.
I've been using adwords for years. Never seen a problem with it. This is nothing new, it's been like this forever. It's pretty obvious how it works in the UI :/
Maybe it should alert you if you resume deleted campaigns and ask if you really meant it.