And that is in part because scientific inquiry as an enterprise rests on logical thought processes. The notion that a "person" suddenly pops into being at some arbitrary point along the way of the already-in-process development is anathema to logic and common sense, and therefore incompatible with science. The only room for this is at the relatively unremarkable event of conception, at which point a third DNA-type, distinct from the mother and father, clearly and unmistakably identifies a third organism.
No prescriptive religious dogma is involved. Any rational person with an average IQ should be able to understand this. Pardon the pun, but it isn't rocket science ;)