Late bfp's?

Monica • 🇵🇹J.N.M.V.🕊🇵🇭
I've been reading a lot of posts/forums online and I see a surprising amount of women commenting that they didn't get positives until 19dpo or later, even when they started getting pregnancy signs early on. Why would it take so long to get a positive? Because their cycles are longer? And these are even from tests done at the doctor's office.