They aren't negatively judge by some people, and to the extent they are, they are probably able to overcome negative first impressions by being competent and/or intelligent and/or pleasant. Not everybody is in a position to do that.
If they have the intelligence to get a JD or MD, the cost of an inoffensive tattoo is usually going to be small, particularly compared to their earnings. To the extent it ever cost them significant compensation, they'd likely never know b/c it wouldn't be communicated to them why they left a negative impression.
Exactly. Again, if you are looking at jobs at or near minimum wage, you don't need to be doing anything to further limit your options. A disinterested observer could probably pretty accurately peg who is really going to have no trouble overcoming "normal" tattoos and who needs to maintain every advantage they can by the time they're 16. Of course the 16 year old or 18 year old or 22 year old that can least afford to add any potential disadvantage is exactly the type that would be least likely to recognize that fact.