Yes, I agree, but if all the messages of the spammer, as well as his account, have already been physically deleted, then the meaning disappears.
Yes, I do not delete ordinary users, I disconnect their accounts. Spammer accounts are first blocked, and after a year or two are deleted, so as not to occupy the vacant names to register new users.
P.S. And yet, there is a great wish to give the Administrator the opportunity to clean the logs, for convenience and opportunities to use them at his discretion. There are people like me who really like the order and cleanliness of both the forum and the log who relate to working on the forum very reverently and scrupulously.