This is not on by default.  Our forest functional level is already at 2016 level.  Read the article on how to enable the recycle bin for AD.  Could be useful for admins if they accidentally delete something...

https://docs.microsoft.com/en-us/windows-server/identity/ad-ds/get-started/adac/introduction-to-active-directory-administrative-center-enhancements--level-100-