Some jobs will always be "tip" type service jobs, and some not. Servers and attendants on a ship will always be. Personally, even if the tip was included etc, and i liked the job that they did (which i usually do) then i would tip extra anyway. It's my way of saying "thank you"
I wish tipping was allowed in my profession (....my mind is racing now)
(PS- if I use the "F" word in my post maybe the double lines will appear under with a link to ........)