Stratolaunch is one of the four largest aircraft
 

The saddest part is, large planes struggle to survive for long,, or they operate very rarely,, May be due to economy issues.

And the point is?
 

Given that SpaceX can launch anything cheaply and land on land anywhere or at sea, what exactly is the point of this beast? Blue Origin has yet to reach orbit but when it does it will also be cheap. Using this beast to launch a rocket from 35000 feet seems silly now

And if they have to land on the reciprocal? :)

The delta-v speed acquired in low atmosphere is the most expensive in terms of fuel factor, mostly because of drag.
For most rockets, the dynamic pressure starts to decrease around 13 km of altitude.
To put things in perspective, the burn-out altitude of Ariane V solid rocket booster is 66.7 km with a speed of 2020 m/s. For a smaller rocket like Atlas V 551, it is 37.7 km. So, for an even smaller rocket, starting from stratospheric limit can mean avoiding the complexity of attaching a solid propellant rocket.
Also, when climbing to a LEO orbit, the decrease in geopotential energy is almost linear. This means that starting from 10 km is a 2.5% saving on geopotential energy.
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While true for the other 3 aircraft listed in the video, I think you'll find the Boeing Dreamlifter (aka Large Cargo Freighter or LCF) and Airbus Beluga stay quite busy. Average utilization for the Dreamlifter fleet (four aircraft) is around 1000 hours/month.

Stratolaunch is an interesting (and valid) concept, but I wonder if anything will ever become of it, especially after the death of Paul Allen.