Maybe that'll help make my point clear for you.
If you're too lazy to go back and actually read the thread that you are posting in, nearly everyone posting tips and has provided their suggested amount.
Finding people that say they don't tip is pretty much impossible.
Your argument that "tipping isn't customary" is dead. It has no data to support it and overwhelming evidence in the form of dozens of people saying "I tip this much" and precious nobody saying "I don't tip" that tipping is in fact customary.
Sure, the plural of anecdotes isn't data, but you don't seem to have a problem with that when one post later you're asking people about what they see in the dining car.
If you don't want to tip, don't. But "nobody else does either" is patently false.
Ah. I get what you're saying now. And no, I'm not "lazy", it just didn't occur to me to take anecdotal evidence from this one thread on a train forum as "data" on tipping. And, now that I do understand what you're saying, it's STILL not data, and I'm still not going to do as you said, because it still doesn't make sense.
First of all, what you're hearing in this forum is self reported. People WHO TIP - and feel like posting about their tips - are reporting what they tip. We're not hearing from everyone on this forum, just people who feel like chiming in. Secondly, this is is a forum for train regulars. I would be surprised if there were many people - if any - who don't tip in the sleepers. People here know the ins & outs of train travel (and what the SCA's job is like), know the SCAs by name, etc. To really figure out what percentage of all train travelers are actually tipping, you'd have to look at, well, all train travelers.
So, just for fun, I googled "Amtrak tipping", and found several articles and discussions (outside of this forum) about tipping sleeping car attendants. And in almost every article/discussion, I found people who said they didn't tip, or that you shouldn't tip.
So, let me summarize my point: we know for certain that some people tip. We know for certain that some people don't tip. What we DON'T know is the actual percentage of people who tip, and whether that percentage is large enough to be called "customary", and so "customary" that an international traveler who is unfamiliar with American tipping customs should be made to feel bad for being uncomfortable with the way we do things.
You can keep saying "It's customary, and that settles it," but it really doesn't. You can boldface, highlight, use pretty colors, and yell at me until you're red in the face, but none of this is actual EVIDENCE. You can't persuade or argue data into existence.