I might be wrong, if it is so please correct me - I'm not relying on sources here, just using my mind, and as we all know, without proper input the output can't always be trusted. I was just wondering, as at least to posts above mentioned the peculiar ability of swords to block hits.
Now yes, I am aware that a spear is not really designed for blocking. But is the blocking ability of a gladius really of decisive value? I mean, it is not much longer than half a meter / shorter than two feet. So it lacks not only the length, but the cross guard of later types. It might be more useful in a sword vs. sword-duel, but against spears? Anyway, in most cases the blows are supposed to come (as seen by the defender) from the left, which is your shield arm.
Arvst