We've established it because you don't die. You're still alive. That makes it nothing like real death because in real death you're not alive at the end of it.
That has nothing to do with the subjective experience though. For all we know, actually dying might be a really similar experience, but of course with a very different outcome. Outcome does not equal experience. An experience is something someone experiences, it's a subjective thing and not necessarily related to the actual reality of the situation.
Note that I don't actually believe the experience of ego death and actually dying actually is similar, I would bet they're quite different. But again, like I said, that's not the point. The ego death is a subjective, psychological and emotional experience that is believed by the experiencer to be real death, hence the term ego death. I think the term is quite fitting and rings with anyone who has actually had the experience. I can understand not getting it if you've never experience that, but you have to face that you simply haven't had the experience, really, you're not in much of a position to talk about experiences you've never had.
But that's simply a delusion isn't it. Other people think they can hear aliens talking to them when they're high. How can you think you've died when you've tripped a thousand times and come back alive every time? Surely the penny must drop sooner or later..."Dude, I think I've died...whoop...nope...I'm just tripping again!".
Yeah, it is a delusion, but that doesn't make the experience any less real during it. Your experience is your entire reality, so while you're believing it, your reality IS that you've died or are dying, and so the resulting psychological/emotional ordeal is very real for you.
But surely after you've experienced it half a dozen times you get the hang of it and realise you arn't going to die?
Nope, because the situation is different each time it actually happens. Yes, I have had trips where I started to hit that loop but then I caught myself, thought of my previous experience, and realize I was just freaking out. But the first time it happened to me, I simply thought maybe that was some sort of adverse reaction. Then the second time, I believed I had overdosed. Then the third time, it was simply 100% apparent to me beyond a shadow of a doubt that I had gone too far and had undone reality. Of course that wasn't really happening, but all of me believed it was at the time. The reasons were different and compelling to me at the time beyond any doubt, even though similar things had happened to me before. My mind was so altered that it became possible for me to believe such a thing, even when I had believed it before and realized afterwards that I had been wrong.