I don’t actually know, but it may be down to covering more space or more angles. I does seem to be a thing though, you’ll notice as soon as you start sparring with sabers, particularly extra curvy ones.
In our club I’ve noticed a given bout with a longsword takes between about 5-30 seconds, maybe up to two minutes if both fighters are good and being very cautious.
A rapier (alone) match is about the same.
Rapier with dagger is about double a longsword.
Sword and buckler is about the same as rapier with dagger.
Messer fights are also about the same.
Bouts with sabers tend to go from the usual 5 seconds to about two minutes, I’ve seen them go as long as ten minutes, with multiple short bouts of exchanges followed by circling.
This is in part because a saber is better at defending with than it is at attacking, a fight with a saber vs. a longsword won’t last so long for example. But sabers do seem to parry well…