Why have these apps been removed?
Google also updated its guidelines in April this year and said that it is expanding Play Store’s Target Level API requirements. What this means is that new apps and updates already have to “target an Android API level within one year of the latest major Android OS version release,” or they cannot be published.
With apps that haven’t been updated, there is always a risk of security. If apps aren’t updated then they don’t get security patches and will also have bugs that can be problematic. Also, if a developer is seeking revenue from advertisers then the app would need to be updated regularly.
The delisting of the app just leads to it being removed from the App Store as users who have downloaded can still continue to use them on their devices.