It doesn’t take much to notice that getting “inked” is very popular these days. Some tattoos are so small that one barely notices them. Others—from athletes to actors to everyday people—have opted to cover much of their bodies with multicolored inks, words, and designs. The trend seems like it’s here to stay, a trend that netted $3 billion in revenue in 2014—and an additional $66 million for tattoo removal...