Just read the flavor text. It perfectly describes entirely his function as a Dude in Doomtown. Steven Wiles is great in every deck with the exact purpose of getting something done on the cheap.
Use him to stall your opponent's win by a turn by bringing in 3 Influence for 1 ghostrock.
Use him as a studly cruise missile to assault, harass, and even intimidate your opponent. What does it matter if he's a casualty, he's going away the next day anyway..
Use him to steal control of a pivotal point of yours, or block an opponents deed from production. He doesn't get paid or discarded until after production.
Bring him back from discard with Hired Guns if you want to hear some groans from across the table.
All in all, a great dude to have on your side of Doomtown.