Samba is the wrong tool to share between linux boxes. NFS is much much better. Samba is great, but it is a reverse engineered system, wherein *nix computers try to emulate windows networking. NFS is native to *nix, and fully open. There is no emulation of another system going on. You'll see much better results and have a much easier time using NFS between 2 linux boxes than you would with samba.
It's a similar to asking why don't 2 Chinese people talk to each other in French. If they both know French it is at least possible, but Chinese makes much more sense as the language of communication between them.