Jedi Cannot Wear Armour is one of those quintessential Star Wars conventions, and by that I mean it's got this weird disconnect where if you say that you fancy having Rey, Finn, Jannah and the OCs don armour for really dangerous missions, people will write you essays on why that cannot possibly happen, then get into lots of specifics of why special metals weigh far too much (not that this stopped Sabine doing acrobatics or indeed did much to slow down Phasma or the Praetorians, among others) but really the main reason is just that once upon a time, George Lucas didn't really fancy doing that and wanted to have them look like Obi-Wan's OT robes.