Yes, we couldn't think of a realistic use case where someone would want to reinstall but use the existing database.
If you are updating you can just copy over the existing files. Since the primary purpose of the installer is to set up and insert data into the database, we didnt' think supporting installation with the same database made much sense.
Is there a realistic use case where you think that might be desired? I think in your case you should just overwrite the old files and wouldn't need to reinstall at all.