It's not like either Lee or Kirby were camera-shy. We have a number of pictures of Jack with his other noteable business partner, Joe Simon, and many more with his wife, Roz. And, geez, how many tons of pictures can you find of Stan with a quick Google search? Hell, part of his schtick any more is making cameo appearances in Marvel movies!
So it makes me wonder why they were so rarely photographed together?
I mean, two photos? That's it? I have literally seen more pictures of Jack with Linda McCartney, who he only met once in 1976, than I have of Jack with Stan.