I want and NEED good traction especially at big speeds,
Good suspension allows this,
Rigid does not,
I like my tires on the ground and feel no need to take a beating from my bike.

Yeah Yeah I get it, I To have heard the stories starting to pop up and now an article in the MBA rag about how on some trails under certain conditions full on fat bikes are turning in times faster that regular old out of 'Style' 2.2-2.35" wide tire'd trail bikes..

As for the weight of a full squish bike,,,PfFFfttt
If I was a weight weenie I drop 10 more pounds of my self before I'd spend big coin to drop 5 off my bike,,,

BTW after riding two I am beginning to think 27.5 plus bikes when set up right may be as good or even better under MANY different trail conditions (but not all) as our tried and true ,,, again per the manufacturers, our out of style trail bikes.

The next, 'greatest thing' does sell bikes but don't forget that a short while back the next greatest thing was the 29er and it turns out It was one of the greatest things.....