Unfortunately a lot of data retention policies aren’t so mechanical, but are of the form “delete after 7 years unless there is a legal hold in force”, which is

Unfortunately a lot of data retention policies aren’t so mechanical, but are of the form “delete after 7 years unless there is a legal hold in force”, which is usually just rare enough of an edge case that orgs evaluate it manually and hence only do periodic manual purges. But probably the main reason auto-delete isn’t popular is because a process that can delete your old data is one bug/misconfig away from deleting your new data too.