Answered previously “Great bascinets rigid neck limited turning one's head (at least in English examples, one can turn one's head -inside- the helmet, accoridng to armour historian Tobias Capwell, who has worn one). By contracts, sallets gave the wearer a fairly free pivot around their neck. The visor could be worn down in situations of acute danger, or up for air and vision. The long tail protected the back of the neck without restricting movement. In short, sallets were supremely -flexible- helmets that offered a good combination of visibility, comfort and protection. “ https://www.google.com/amp/s/amp.reddit.com/r/AskHistorians/comments/4gs6v5/why_did_the_sallet_helmet_become_near_universally/ Shoutout to u/WARitter for awesome explanation