Use of database for SCM

[tnorth at bluewin.ch]

Hello,

Here is a question that I really have to ask :) It may be stupid, because
of my lack of knowledge in SCM, but let`s go anyway...

I was just wondering why nobody (as far as I know) uses a database like SQLite
to stock patches and/or patches informations.

Is it because it is easier to work with a file tree ? 
or because Unix` philosophy is "file-centric" ?

I know the use of a DB would certainly bring more complications, but what
about speed ? (is maybe the only profit we could have)
SQLite seems to be very very quick...

Hope that was clear enought !

Have a nice day, and thanks for your amazing work I often use with satisfaction,
TNorth