It's a fading art; the sign painter's stylized, indvidualized visions have largely given way to standardized plastic cutouts, quick, cheap...and empty.
Maybe that's what you want for a sign that says "NO SMOKING within 8 feet of door by state law." Conversely, it's a lousy way to get the name of your business out there, though the handful of clever artists who put die-cutter "printers" to work in an original way do a little to buck the trend.
Standing right in the middle of the avalanche armed with little more than a brush and perhaps a stencil, America's remaining sign painters are doing their part and more -- you can find examples in my neighborhood, Broad Ripple (Good Morning Mama's, outstandingly so). You will find even more examples and, better yet, exemplars at The Sign Painter Movie, a documentary with a fascinating trailer and a long, linked list of folks busily employed painting signs.
It's a rare trade and a unique skill; I could wield a lettering pen well enough, long ago, but a brush? That's a whole different art: a pen will guide your hand; a brush requires piloting.
(Link found at the blog of one of the better-known underground comix artists. Not unsurprisingly, if you think about it.)