I think the HALO is the next logical step after the steps F1 took the last twenty-five years, what started with San Marino in 1994. A halo on a '95 car wouldn't have made much sense, it's the combination with the cockpit sides, the HANS (remember all the "oh I can't race with that thing" stuff that was going round?), strengthening of the safety cell, impact structures, etc etc.
Just in the years before 94, F1 has been lucky that that one important bit that was sticking out of the safety cell, unprotected in big crashes, didn't cause more injuries of deaths, like we've seen in other racing series.
Most people also forget that the 1994 season almost ended formula one, dying racing car drivers isn't good for sponsors and TV.
I like the simplicity of the HALO, it's relative cheap and will make a great change in safety especially in lower racing series, where additional safety features like wheel teathers and f1 style trackside safety are non existing.