WPS has two modes: the button and a PIN. The PIN was implemented first because it’s the most convenient and doesn’t need hardware and it turned out to be a sec

WPS has two modes: the button and a PIN. The PIN was implemented first because it’s the most convenient and doesn’t need hardware and it turned out to be a security disaster. So now its reputation is shot and for both PIN and the button there had to be a way to turn off WPS (with the ‘secure’ default option being WPS off)