Android updates are just as important, because Google is working on the performance of the OS itself more and more. Project Butter isn't through.
They aren't just as important. With Android those system updates will fix bugs in the OS sure, but they won't update apps like the browser, email etc. Those are updated separately by the app store. With iOS those updates also contain updates for the apps as well as system updates? Want to update Safari? They have to package a system update.