The problem is that "GMO" is not a useful label. Maybe it means you have 20x more vitamin A, or maybe it means it contains BT, or maybe it means it was grown in a pool of roundup, or maybe it means that it's got back a missing bit of chromosome that got lost during selective breeding. It's about as helpful as "made with select varieties". It's _not_ like "from cows not treated with rBST", because this is a very specific chemical that has a particular effect on cows.
You could also add: "warning--this food may have been processed in a facility where some workers have AIDS." It sounds scary and doesn't help you decide anything.
"Warning: the contents have not been screened for lethal concentrations of polonium." Uh?
"Warning: the contents have not been harvested in a topsoil-neutral manner." Yeah, pretty much everything.
"Latitude 40+ product inside." Well, maybe true, but why do we care?
"Packaged in a facility that includes atheist workers." Can we trust them?
"Contains machine-processed ingredients." Oh no! You mean people didn't hull the wheat by hand?!
If GMO labels said what the modification(s) were, then it would be meaningfully more information. Pandering to panicky trends is not providing more information in a meaningful sense; it's inconveniencing everyone. If there's a market for GMO-free food, fine, there should be regulations to make sure that means what people think it means so that at least it's honest. But when you want something that is not well justified, you should be the one to go out of your way to get it/advertise it.
(Personally, I would really like to know what modifications were there, but unfortunately I think the chance of that happening is close to zero.)