Well, unless somehow they failed to think this through (which I seriously doubt,) they have decided that both the government, the airport and advertisers have no liability concern here.

Meanwhile, McDonalds has to tell its customers that coffee is hot...

You're right, the issue is liability. But what I don't understand is why what's right and good, is of no concern...

Not to mention that it would be next to impossible to prove that the sign caused an accident. Though of course the gov't doesn't need to show someone ever endangered anyone before being able to issue a $500 fine for texting.