The reason swords were more commonly used jthen say a mace or axe by professional /semi professional/trained fighters (as opposed to temporary militia) is that it is more versatile. It is also easier to carry and any weapon you can get your hands on is ALWAYS superior to a weapon you don’t have. Add in that the sword is (in general) a faster more maneuverable weapon then pole arms and maces and axes and such. And this maneuverability is a huge help if you are indoors. So as a general side arm the sword was easier to work with in most non combat situations and also in personal combat vs general battles. And any given person spent more time out of combat and going about Thier business and or indoors then they did outside in a big battle. It is the same basic logic for why pistols are uses for concealed carry personal defense and by police officers as thiere standard carry side arm vs a long gun/shotgun/rifle. The long guns are better weapons but they are not as useful/versatile/easy to carry. And a sword is more able to be used defensively as well as offensively. let’s see you parry with a battle axe, yes it can be done but not as well as with a sword.