I guess sudo service samba stop would have been too obvious. So, they chose something less intuitive. Wouldn't want to make things too logical or easy.
In the beginning of time there was the smbd daemon and the nmbd daemon. Some smart folks over at RedHat decided to combine the two into one "service" called "samba" since System Administrators tend to run both in sequence. In Debian it's still that way.

In Ubuntu ( I think because of upstart - not sure ) they went back to the olden days where your run smbd and nmbd separately.