| The probe is 2.7 million miles from Jupiter, headed further out (its orbit is highly eccentric). That's nearly 11 times the distance from the Earth to the Moon. At closest approach, Juno will be 2,200 miles from Jupiter, less than 1% of the distance between the Earth and Moon. Space exploration is expensive, and a very large part of that expense is mass. Putting a 2.7 million mile scope on a probe that's going to be spending much of its time far closer in to interesting targets costs mass, and fuel, and other sensing apparatus you can't add. So there's that. It's possible that there are higher-resolution capabilities for the probe as well, or that post-processing or higher data rates will improve current images. It's also possible that visual reconnaissance wasn't a high priority for this mission, though I'm not familiar with the sensing platforms included. Given orbital eccentricity, Juno can acquire and store high-quality data, and transmit that at leisure during the outbound parts of its orbit. |
And yes, photos weren't a priority at all. If it were just a matter of returning scientifically useful data, they wouldn't have included this camera at all. But NASA likes pretty pictures too, so they included one.