You're right in that art is guided by a different set of goals than client work -- it's inherently more exploratory.
But it's inaccurate (and unfair) to call it imprecise. (Also unfair to assume artists work "randomly.") If you're an artist who cares about your work, you put a tremendous amount of effort into achieving your vision just as you see it. If a tool fails to work as you need it to, you'll abandon the tool, whether it's a paintbrush, a chisel, or Max/MSP.
The fact that two major commercial sound programming environments are visual doesn't necessarily mean people who use them don't understand computers and are just randomly throwing crap at the wall: It means they work best for the professionals who use them to get their creative work done. They are, after all, relatively expensive pieces of software.
(It's also inaccurate to assume artists and musicians don't ever have programming ability. I'll point to myself as an example.)