This may seem like a no-brainer as styles go, since logically anyone that can write AND tattoo should feasibly be able to do this style by simply combining these skills. But like much of life, many artists refuse to let it be as simple as that, and in the process become avid typographers in their down time. The next thing you know they’re messing with ascenders and descenders, adding and subtracting serifs, underlining words and crossing T’s with loopy filigree, adding drop-shadows and shading, and blending aspects of completely different fonts into one hybrid style.
At a certain point, letters stop being as simple as a collection of symbols communicating an agreed upon sound, and become art in their own right. It takes a little more time and effort, tasking an artist with essentially making up a new alphabet, but the results are well worth it.