I notice that this service is not started in ubuntu 18.10 and, it seems to slow down the boot process on older machines. Since Samba is not installed, what is this service for?
samba is part of the UB seeds - so it is installed by default.
It is part of the network layer of samba.
If you are finding that this is slowing down the boot please report the issue against the samba package
I’ve seen similar issues on debian and it is certainly fixable.