Now that you mention it, it kind of makes sense.

I'm not convinced there isn't a lot of optical illusion involved in looking at saddles ... but there has to be something to support the rear of the saddle. If it's a monocoque shell then there's an awful lot of torque on the sides unless the transition is more gradual, to distribute the load. If it's a tensioned leather saddle with a cantle plate, then you have all the weight that entails.