Well, the problem with believing in an afterlife is that you essentially HAVE to accept that there’s a supernatural explanation for it. Simply put, if it exists, there is no way to study it because a person has to be dead in order to experience it, and we live in such a modern world that by now nearly all of life’s mysteries have already been explained scientifically. In order to accept the afterlife as being real, you have to accept that it can’t be objectively explained, and that’s where a lot of doubters probably encounter their difficulties with the concept.
As to your statement about these NDE’s being a result of brain chemicals and some such, then how do you explain this video? The woman here was brain dead for quite some time yet she had this incredibly intense, profoundly “real” experience of an afterlife (she was even able to witness and listen to the surgeons in the operating room in spite of having her ears plugged). Even the physicians in the video say that, because every measurable aspect of her body & brain indicated that she was dead, the woman should not have experienced what she went through, and the doctors have no explanation for it. How do you explain something like that?