What protects you in that scenario is those apps aren't really vulnerable to leaking anything in the first place. Malicious ads in games can only see what other ads you've viewed, it's not like you're signed in to your bank website in Angry Birds.
And if your banking app with its embedded webview has its site compromised, you're already fucked without even opening the app.
And if your banking app with its embedded webview has its site compromised, you're already fucked without even opening the app.