Here's the advantage of vulcan after wiff.
If you were to cancel and move forward:
After canceling, vulcan punch will not come out where you stand, the active frames act as a shield that is about a characters distance from his body. Furthermore, if you cancel this way it will transport Ralf about a characters distance from his original position. This means a rough 3 characters distance forward, well, more like 2 and 1/3, still good enough.
Considering that thid acts as a shield for his whole body (it will even punish Kensuos sweep if not too far) and since the active frames will be in your oponents face this will act as an anti air, anti hop, anti non invincible specials and punish most mormals and lows.
Keep in mind, Ralf does not have many reversals, but he does have 20% more guarde bar.