Question should be clear from its title. For example Apache saves its access and error logs in files instead of RDBMS no matter on how large or small scale it is being utilized.
For RDMS we just have to write SQL queries and it will do the work while for files we must decide a particular format and then write regex or may be parsers to manipulate them. And those might even fail in particular circumstances if great care was not paid.
Yet everyone seems to prefer filesystem for maintaining the logs. I am not biased against any of these methods but I would like to know why it is practiced like this. Is it speed or maintainability or something else?