The moment they are created they are out of date.
The second you send out the file with the attachment, they are old.
When you go to revisit them two weeks later and you need to change all the tasks because the project has changed, they are rendered useless.
When the dates don’t line up to the work that is being done (because not everything has been written down) they miss the point.
That’s the problem with Project Plans.
Fix that and you’ve got something of value.