Because no, we don't. Mortality is a thing that souls can experience, but it's not all there is to existence. Feeling forced into it is such an American idea, a Western idea, a really rather bad idea. Indeed there are whole religions that explain how to break the cycle of reincarnation, for those who wish to do so.
“I’ve attended funerals of, let’s say, four close friends, one of whom was a writer.” He wasn’t prepared for any.
“The plan goes like this,” he explains. “Your grandparents die. And then in time your parents die. The truly startling thing is that your friends start to die. That’s not in the plan.”
But of course it's the plan. Once you incarnate, there you are, until you die. That's the name of the game. You get a body, you wear it out, you either get a new one or decide you don't want to do that right now.
What makes people miserable is treating this as a bad thing. If you don't prepare for childbirth, it tends to be dangerous and horrible. So too with death, and that's mostly what we have in modern America, which sucks for everyone, because unlike childbirth, death is not avoidable once you are alive. If you prepare, however, then the event becomes exciting. It may still be uncomfortable, but it is unlikely to be a disaster unless things go very wrong. The process of preparation improves the chance of success. There are good deaths to be had, a variety of them.
So think about what you want, what you don't want, and how to aim. In particular I note that America has gotten into a habit of staving off death at all costs, which means that the things people die of are mostly the ones that can't be stopped at all -- and most of those are horrible ones. Lots of people spend the last year or more of their lives in misery, because they won't let go, or others in power won't let go of them. There are lots better ways to handle this challenge. You don't have to be like the three-year-old who hasn't figured out that being exhausted sucks and sleep is refreshing. Which brings us to some other religions that like reincarnating just fine, consider people immortal just not all at once, and thus view death as a transition rather than an end.
If somebody's batshit ideas make you miserable, you are not stuck with them. There are lots of other options. Try some. Because splatting into the end of your life with no preparation sucks.