Tipping abroad when on holiday is something (from memory - not been abroad for years!) I do do, but very selectively.
I was at a lovely hotel complex in Cuba quite a few years ago and I watched the Bar Staff seriously raking in loads of money from the guests while the rest of the staff - maids, cleaners, ground staff, etc, were typically forgotten about it seemed.
While not strictly speaking "tipping", I used to empty the mini-fridge in the room every morning and hand out all the drinks to the various ground staff (furtively as they were not allowed to accept them really).
At the end of the holiday I did tip the room maid/cleaners as well but reckoned the bar staff were well enough taken care of!