You want to change the root (and mobile!) passwords of your iPad if you install OpenSSH or any other open-up-you-iPad-to-outside sources software.
For OpenSSH, your iPad is, essentially, broadcasting and is visible to someone on the same network. It could happen that someone could gain access to the iPad.
Changing the password removes the ability for someone to accidentally/maliciously access your iPad by merely typing in the default password - which everyone know.
The chances are pretty slim that it could happen [again] - but a while ago a guy wrote code to access iPhones that didn't have the password changed. It was a simple hack to "teach people a lesson" that got a bit out of hand.
Anyway, changing from default passwords is always a good thing... And, with Mobile Terminal - an easy thing.
Marilyn