There were allot of influences on writers "in my opinion", that were outside of bombing. And allot had to do with commercial art and illustrations. I remember even watching Bodega (Spanish grocery stores) sign painters and seeing how they did simple lettering with shadow effects. And I remember in the early 70's my sistas friends teaching me gang/ hippie style letters and coloring. Everything from album covers to soda bottles. We started studying every type of lettering we can find. And all we were trying to do is make our letters more stylish and funky. Simple styles were harder sometimes cause you can't cover up your basic style with arrows and hookups. That's why it's important to learn simple styles first. Then add all the hookups. Allot of times I see pieces that might look nice to beginners, but to me it's just wack letters with allot of hookups and fancy colors.
Any ways, here are some examples of what I'm talking about:
COMIC BOOK LETTERING
BODE'S CHEECH WIZARD LETTERS
BODE'S TEXT LOOKS LIKE A TAG STYLE
COMMOADORS ALBUM COVER
SOFT DRINK BOTTLE LOGOS
and many more influences