Service is down to the people who offer it and also those who receive it; it doesn't matter a jot whether the tip is charged to your shipboard account or not. Does a person who gives good service already know how much you are going to tip? Obviously not! In my experience it also depends on the nationality of the server; some are far better than others. I can remember being in a restroom in a Bangkok hotel where one persons job was to turn on the taps in the basin, offer the towel and then turn the taps off again. He neither looked for nor accepted tips and it was not a 5/6* hotel. Equally I recall drip mats with "customers make pay days possible" as the message and how many people still forget that simple fact? Try being rude to a server and it doesn't matter how much you tip you'll get crap service as you deserve.
And you can add the dreaded baked alaska parade to the macarena as a pet hate and an area where cruise companies could certainly save costs by cancelling.