Why??

Why does everyone say "oh wait till you get implantation bleeding"? Well to be honest with everyone that waits foe it i hate to say it but not everyone gets it only 20% of women who have gotten pregnant got it. I only had it once with my daughter and thats it. Ive had 4 pregnancies and only once did i implant bleed. You should just really wait till you miss your period that you should test. But if you want to test earlier then that cool. But im only asking why do they say wait till you get implantation bleeding.