I can ask the same thing except its the opposite, why Nvidia users feel the need to constantly shout about how bad AMD cards are? It's clear Nvidia users really don't care and have no intention of even buying an AMD card, they feel the need to have everything be in a camp mentality, a distorted view of everything must be a brand war.
The back and forth is getting very old I agree, but you can thank the tech press for pushing this sort of panic and FUD with AMD articles while at the same time pushing tons of hype and praise for Nvidia, and the users get upset when something doesn't launch when they think it needs to.