Originally Posted by Kapusta

This may be a semantics thing, but think it IS getting the saddle out of the way. When you try to get low with the saddle all the way up, its in the way of you getting low. A dropper gets it out of the way.

One piece of common wisdom that has changed in the last decade is rather than “low and back”, the emphasis now is on just getting “low”. With a raised saddle, you can get low, but only by shifting way back as well. One downside to this is that your arms are in a fully extended position, so you have a limited ability to work the front end through dips, or preload it to pop the front over something, or weight it for traction when needed. In short, having your legs or arms fully extended is bad for bike handling.

Dropping the saddle lets you get low without leaning back, thus keeping your weight more centered, and also allowing you to keep your arms bent which allows you to work the front end of the bike up and down over obstacles.

I will occasionally sit in the dropped position, but only to get a rest on a mellow DH section of trail. There is no performance or handling reason to do it that I can think of.