why is it when I record a song in logic Pro, it also goes to the trash

Logic has an automatic backup feature, so that if the Mac crashes, you may have a good chance of re-loading the project you were working on.

After you save a project file, the backup is no longer needed, so it is sent to the trash.

I am pretty sure that is what you have noticed.

When you are recording in Logic, you keep some takes in the session & reject or abort some bad takes. The files you are finding in the trash are the aborted takes. When you abort a take in Logic, it automatically goes in Trash.