Considering this answer which cites a halacha that Cohanim must duchen together, I'm curious as to why so many shuls that I have attended throughout many years seem to have a group of Cohanim that don't coordinate the duchenin. The Cohanim are not all singing the same tune, they're not in the same tempo, and there are one or two Cohanim that say the last word of each verse a bit after the rest of the group so it sounds like there's an echo. I know that the Levi'im had a choir in the Bet Hamikdash, and they had a conductor. I assume that they had some type of rehearsal, or even if not, they were better coordinated. At least there's a precedence for nice music during tefillah. I would think that Cohanim would care to sound coordinated, at least, if not on tune, as well.
Is there some reason as to why it is this way? Is it a lack of knowing the halacha or carelessness? Why does this happen consistently?