That is merely your opinion. You think that natural sciences - that which can be seen under a microscope, or through a telescope, or discerned through mechanical devices invented by human beings, and understood via imperfect human intelligence and reason, is the only way to know truth.
I disagree entirely.
There is no point of reference that we agree upon, so further discussion is useless.
No other method has even come close.
Speculating about reincarnation doesn't gain one any useful or reliable information about the physical world, but it has the advantage that there is no actual knowledge needed to pontificate about the subject and nobody can ever prove you are right or wrong.
There must be some comfort in that.
Science, on the other hand, is difficult to know and understand and to keep up with all the accumulating knowledge. Far better for some to ignore it and feel satisfied that they know the answers to the questions that they think are important, like just how much I have to think about Tigers before I get reincarnated as one.