My assumption (and assume means makes an ass of u and me...) is that this meant 'Why not add a postscript to your one word or one line reply?". However, in modern day Millennial Undergraduate Texting Talk External Reply (MUTTER) everything gets abbreviated, where the number of question points (3 in this case: ???) indicates something of the anxiety or patience of the poster for further eloquent elucidation. I am not capable of such expansion as I only have timeshare on a neuron and it's not my turn this week...
"Why not" is not a code actually. I meant why not we also consider clinicians while publishing an academic paper because they may apply the findings for clinical purposes. I hope it is clear now.