Yeah but then you have to redownload it, log back in, get your settings back to how you want, etc.
What I think should be required is a "clear cache" option by default in apps. Two of my apps, Tumblr and Flipboard, have them, and its really handy in those two as they can collect data up real fast, so to be able to reset the cache at anytime brings those apps from 300-400mb of storage used back to 80-90.