I can absolutely accept that there is a difference between looking at a screen and staring at it. My eyes probably can't do it because there's so much difficulty shifting between near and distant vision, but that doesn't mean it's unreasonable for you to do it.

The texting comparison that others in this thread are making doesn't seem to me to fit very well. Photography is generally going to require you to keep aware of your surroundings and to literally watch where you're going. I assume there aren't a lot of cyclists trying to shoot things that are behind them. Texting, on the other hand, clearly detaches and distracts you from your surroundings.

There are, of course, some things that absolutely never be done on a bike. One should never juggle sharp knives on a bike, for example. I just don't think photography belongs in that category as long as the photographer remains situationally aware.

BTW, bicycling inherently requires divided attention. We are attending to steering the vehicle as well as providing the motive power ourselves and maintaining balance. I noticed there's a certain mental tiredness I get after a long bike ride that I don''t experience after a long drive, and I think it's the result of constantly having to scan the ground ahead for potholes and other small obstacles.