Because he's damn good in action, yeah people will connect he's not good enough or he don't have physique for that or the look but anyone with brains can tell that all these things are just bunch of nonsensical talks.
He's always been good in action, he just did action movies less and even in those movies where action is less you can see that he is infact good in that.
It's not just about punching and kicking or muscles, it's shit emotions too and intensity, which are required won't with choreography to make an action scene great looking on screen and SRK has that covered, and even then people had misconceptions that will he suit more massy type action, they doubts were answered in Dilwale & Raees which weren't good movies but SRK himself was good, more in Raees obviously.
Although i don't want action like Dilwale, it doesn't look good but one thing was shown that SRK can sit that type of stuff too even if it is not something which i prefer.
So all this nonsense is just as i said, Nonsense, SRK has always been good in action and different types of then too.