Simply not true - as long as you don't use internal APIs, apps made for an older Android are completely compatible in newer ones, and new APIs are usually backported to older Android versions with compatibility libraries. When you update your Android OS, all of your apps will continue to work the same and you don't even notice.
Contrast this to iOS - whenever there is a new iOS version, developers have to scramble to update their apps because they very often break or the UI is broken by changes, etc.
Android is much much less hassle when OS updates roll around, and I develop for both.