@fogcloud ssh in 1.5.10 and earlier isn’t required for anything but it will be required for 1.6.
After such a long time of using ftp I made a switch to prefer using ssh instead as it is generally more secure and can eventually (hopefully) be extended to allow Pki authentication which we cannot do for ftp based things. Plus it gives us much more utility than ftp provides.
I know you weren’t looking for a book on this all.
TLDR, no it’s not “required” but is effectively a default standard in dang near all operating systems now. It shouldn’t hurt anything, for now. In the future it absolutely will.
PS If you are worried of subnets gaining access to your fog server, use a firewall to block those subnets. I would highly recommend not blocking the specific port for ssh.