I've got a question about databases: why don't they use raw disk partitions instead of files? If you think about it, a modern disk filesystem is really a form

I've got a question about databases: why don't they use raw disk partitions instead of files? If you think about it, a modern disk filesystem is really a form of database (but not the relational kind): various kinds of data (filename, date, access time, etc., and finally the actual data) are stored in a schema on the disk (which itself is abstracted by the disk controller) in a way that it can be looked up and retrieved quickly. Most modern databases I've heard of use regular filesystems to store their data, so it's a database using another database to store data. Wouldn't it be faster to eliminate the filesystem altogether, and just have the SQL database go directly to the disk, just like Linux swap partitions do? After a little googling, it does seem that Oracle used to do this (but no more), and MySQL's InnoDB still offers this. Others claim that there's no advantage to this because the kernel handles dealing with raw devices better than the DB does, but I think it's more likely that the DBs just don't have enough development resources to try doing it better; filesystems are necessarily going to incur a certain amount of overhead, so it only makes sense that theoretically you could go directly to the raw device and cut out some of that overhead, though you would be replicating some of what the kernel's filesystem driver is doing, but in a way that's more optimal for the DB.