Inside? or outside? What if a slide wears through the exterior vest shell before you are stopped by an object, or are finished sliding? What if I fall on a trail, and it's immediately punctured by a limb or branch or sharp rock? And what if it's inside, and... see "Ventilation" below.
Ventilation? In the Steamy South, I'm already at my limits with a full face helmet, boots, and a mesh jacket with a shirt underneath. Last thing I need is to reduce airflow any more than I already have.
Algorithm or physical tether? As mentioned, offroad spills can be different than a crash on the street, and you don't want the vest to inflate on a low-speed tipover or a slip, many times you just step off the bike, and pick it back up and carry on. But if I get launched on a gravel road or a rock garden, I'll want some cushion between me and the hard stuff on the ground.
After a deployment, assume the vest is undamaged. So some you have to send away for inspection and reset or recharge (or whatever), and you're without it for ...how many weeks?
And they cost. I am not arguing the potential injuries that may be avoided, but I am a tightwad, and the expense (investment, if you prefer) would go a long way toward additional rider training.
I'm not a MotoGP racer, so whatever my getoffs may look like, it won't be like most of theirs...
These are some of the nagging questions that plague me, and in my mind an airbag vest is not as straightforward a decision as say, a helmet or a jacket or gloves. It's not just find a color you like, find one that fits and offers some level of protection, and off you go.