Ignoring the technical cost, keeing Trash files indefinitely (or for unexpectedly long periods of time) has to be at least a bit of a privacy kerfluffle risk for Google, right? People freak out when they do a GDPR data request and find just how large and long a memory Google has of their searches and locations. They likely would be even less happy finding out Google has held on to files that were long ago deleted for important and/or personal reasons.