Carrier screening covers a really small fraction of pathogenic variants. It'll catch really catastrophic stuff but there's an enormous number of mixed-penetran

Carrier screening covers a really small fraction of pathogenic variants. It'll catch really catastrophic stuff but there's an enormous number of mixed-penetrance/AD variants that people pass on because they aren't lethal. (plus, let's be real, most prospective parents don't carrier screen. only ones about to undergo IVF where PGT-M is sometimes an option.)