Black suits are really not considered business attire - they do make you look like morticians and G-men.
Formal attire is something different. Yes black tie does call for black - but tuxedos rather than business suits. When events go super formal, attire shifts from black tie to white tie (coat and tails, and sometimes top hats and canes).
There's a well-known saying that you should never be remembered for what you wear in a business setting. You don't want to be wearing something so shabby that you stick out in a crowd; but you also don't want to be wearing stuff that is so expensive that the people recruiting you take note (I always leave the Rolex at home for recruiting events). In a recruiting setting, leave everything flashy at home (including but not limited to bright/fancy colors, french cuffs, shoes with buckles, suits with highly defined patterns or stripes, flashy shirts, and so on). I'm really just talking about attire for men; women have a lot more flexibility.
Going back to the black suit, it could cause you to stand out at a recruiting event. Many people will not notice, but there are definitely people that do not regard black suits as proper business attire. You want to do everything in your power to avoid getting dinged before you even open your mouth. Remember, it is never good to be remembered for your clothes at a recruiting event, no matter how good it sounds to you right no.