Stress
Working within the justice system can be stressful—especially for an artist who, let's face it, probably has a hundred times more experience sharpening pencils than engaging in heart-to-hearts with crime victims. The experience of describing an attacker will be far more taxing for them than for you, but that doesn't mean sitting with them will be like sipping mojitos on Siesta Key.
The questions you ask may upset them, and the closer you get to making them remember that face, the more pain you're bringing back to them. Yikes.
"That's not really my scene," we hear you say. "I prefer drawing petite pictures of puppies, petunias, and other things beginning with 'P'." That's fine, but keep that up and you're likely to find another "P" at the top of your mind before long: "personal income."
Work for rōnin artists can be notoriously inconsistent, leaving would-be sketchers with big budget gaps and a few nights a month of staring at the lights chanting, "Please don't go out, please don't go out." Eventually, you might find yourself looking for a part-time job. Or a full-time job. And at that point, would it even be fair to call you a "sketch artist?"