Not sure why it would matter what the customs were in 1966 of a place you're visiting in 2013.
I agree, but the tricky part is knowing what is genuinely expected (in essence, REQUIRED) in the country in 2013. As has been stated before in this thread and elsewhere, in the US the tip, at least in the case of restaurant servers and similar workers who are considered "tipped employees" by the IRS, is part of the employee's normal compensation. Regardless of the historical origins of tipping, it really has little to do anymore with whether the service was exceptional or not. This is an alien concept elsewhere. So the question is what does a tip really mean in a particular place in 2013?
To eliminate the mystery of the local tipping etiquette in places you are going to visit, if a traveler cares enough to want to know, its probably in a guide book, most will always have a section on tipping, experienced travel agents can help you, or there is the wonderful thing you're surfing now just chock full of information and opinions. None of us really need to wait to be told what to do, we can find out easily in advance if we care to.
That is exactly what I do before visiting an unfamiliar country. But general travel advice is often not going to be of much help when it comes to tipping dive industry people. I just reached over to my shelf full of Lonely Planet and Rough Guide guidebooks and pulled out Indonesia. I was surprised not to find anything on tipping (though I suppose I could have missed it). That said, it's clear that the expectation at a local warung is very different from the expectation at a well-known international luxury dive resort or liveaboard. Dive resorts and liveaboards are generally totally different animals from local businesses. But there are many gradations in between the two extremes, including modest dive shops visited more by the international backpacker set than well-heeled Americans. What to do?
In contrast to Indonesia, my Lonely Planet Egypt book has a whole section on the topic of baksheesh--the practice of "tipping" pretty much everyone for pretty much everything, though often in tiny amounts. The section notes that in hotels and restaurants a 12% service charge is included, but one should still leave a little baksheesh for the waiter because the service charge goes into the till. Confusing? I'm sure it can be. It's not clear how this applies to the dive industry. My guess is that because of the baksheesh culture, tipping in some amount is expected by local dive industry employees. How much does one leave? An American-sized tip or what locals might expect based on what employees in other local industries receive? I would leave an American-sized tip in Egypt, but as I said in my previous post, I can't imagine the locals would fault, say, a Scandinavian for leaving something more modest. I just don't like the idea of one-size-fits-all tipping everywhere in the world. As I said, I completely agree with the adage "When in Rome do as the Romans do," but I noted that it's not always easy to know what to do when it comes to tipping for diving. The guidebooks just aren't that helpful when trying to translate local customs into what to do at dive operations.
I can say that here we get planeloads of Aussies and Scandis and almost no Americans, and yet there's a tip box on every boat, so the theory that Americans are "spoiling" locals and creating a tipping culture where one hadn't previously existed won't hold water, at least not here in SE Asia. . . .
The tip box concept didn't just magically occur one day to some Thai who had never been exposed to Western culture. Rather, I suspect the idea was imported by someone who had seen it elsewhere. The presence of a tip box can mean either "in setting our wages, our boss assumes we receive tips as part of our normal compensation that we need in order to survive" (as in the US) or "it would be nice if someone left us a little show of gratitude to supplement our pay." It's difficult to know.
I like the idea of a service charge. If restaurants in some region customarily add a service charge, why not dive operations in that region? One would still be free to slip the divemaster a little extra on top of the service charge if they wished to, but at least people who chose not to would not be criticized by the international dive community as being "cheap."
In reality, the more international resorts and liveaboards these days all seem to make their expectations known with respect to the sticky issue of tipping. From what I've experienced, they are not bashful about addressing it (hopefully tactfully) in their welcome speech or at some other point during one's stay. Smaller operations often don't say anything, so it's hard to know what to do there. In that case, I try to size up my fellow divers. If they're a bunch of 20 year-old backpackers with threadbare rental gear, I'll probably leave a more modest tip than I would if they were well-heeled divers on a luxe liveaboard.