"because then the students would have to attempt to draw what they saw, rather than what they imagined. "
Precisely.
And yes, babies tend to move like washing machine agitators with arms and legs when you try to take a pic.
Or they sit still, mostly, but they look everywhere in a constant skull movement not conducive to good useful photography.
*chuckle*
Babies thrash, unless they're asleep. Or they're spitting up.
Cats, on the other hand, are in "picture mode" almost every waking hour, and if they slip, they resent you for seeing them :-).
With landscapes, you just have to frame and focus correctly, and have the technology to keep your waterfalls from getting blurry.