Because shortstack nl and lhe rely on taking mostly 5-10% edges to win at showdown for most of the value. And its easy to roll a 10 sided die 50 times before you land on the desired number.

Fold equity exists at shortstacking, sure, but generally you are only pushing when you know you are ahead of the range he'll call with, meaning you are taking a modest edge vs villains range most of the time.
pokerstars 100nl full ring players wouldnt agree with that, i just tried em out. They like to flip/call miles behind.