As I understand it, they're where used in combat sometimes and some of them have blades as long as short swords and yet I haven't seen a single seax with a crossguard. Do we know the reason behind this?

One might think that it would be very dangerous to go up against another armed opponent without any protection for your hand/fingers. Was it just because it was easier and cheaper to manufacture or is there any advantage of not having a crossguard on a blade?