How come developers nerf their free apps when they release new paid ones?

[iVenom]

I know its for the money that was more rhetoricle. But I dont think its right to mess up an app then plaster free on it when they come out with a new app. Im sure you all can name tons that did this but my main gripe is with shazam. They have on the app page that if you had it in the beginning you could still use the free on with unlimited tags but no new features ok cool we get grandfathered in, that should be for all the apps, but i have a new iphone 4 restored from the 3gs file and now no unlimited tags. They got me though the page says "current" device. Shouldnt there be a "grandfather in" rule? Isnt it because of us early adopters of these apps even if its free that gets the developer money through adds and buzz so other want to go check out the app? I want to hear what you guys think about this and some developers al well. Thanks