I have never done this and have been doing 1-3 cruises per year since 1982. What cruise line were you on where this was customary? Oh, and when?
Don't know if it ever was customary - But I have been on about half a dozen cruises over the years (mostly carnival), but I haven't been in about two years.
Tipping my room steward on 1st day is just something I have always done (not in lieu of full trip tip just a toke so you are remembered - sort of like tipping at check in Las Vegas) and wondered if anyone else had or still does?