The main reason is streamlining, if you dive in flow this becomes a real issue albeit a bit of a non issue on most wreck dives.
Restraining a wing does mean that holding gas in it is harder if it is holed, just as Mal said. It is also much much harder to orally inflate can lead to unstable iunflation and, yes of course, can snag on stuff. I'm trying to put the reasons in order of my own priority.
Put simply, there is no need for bungies. Just have a wing which is correctly sized. If you want one however, do whatever floats your boat (I understand that moist OMS wings will
) But the poster asked why DIR divers don't do it.
If this must descend into popcorn like most DIR threads, so be it. But given it's a question on a diving forum I thought I'd give it the benefit of the doubt. Do remember guys that there are many other divers who looking at the alternatives don't dive bondage wings either.
Oh and George? Well your anonymous PMer is right that the WKPP did approach existing manufacturers to see if they would make suitable equipment. Divers on the project didn't want to manufacture kit, they wanted to dive. OMS, Diverite and others refused to make what the guys wanted so Halcyon was indirectly created to support the manufacture of suitable kit. Disappointing isn't it when the truth is nowhere near as exciting as the rumour mill