[CentOS] Samba "use sendfile" configuration option set do disabled as default - why?

Hello,

I had problems with speed of Samba, so I was looking for some solution
and I had discovered "use sendfile" configuration option. I was
checking all Samba release notes and I had discovered, that from some
version (older than is in CentOS repo) this option was turned on as
default. So my question is, why in CentOS 5.3 is that option in
default set to off?

Thank you for responses
Martin Šťastný