To be fair, Quora isn't a very graphically rich site. I'm not totally sure whether an absence of Photoshop (and other Creative Suite products) is particularly worthy of explanation.
As a designer who's in Photoshop all day long, knowing when a layout necessitates using Photoshop or not is second-nature to me now. I'll just stop using it and hop over to my text editor and start writing HTML & CSS. And for sufficiently sparse layouts, I'll just not use Photoshop at all. I assumed everyone knew and did this, but perhaps I was mistaken.