Hood insulation: Why? Do you keep it, or don't you?

[Bluestep]

I have always assumed it is for sound dampening, as it was included only in the more upscale trim packages.
I have never heard the fire suppression theory. I don't buy it. If that was the case it would seem that all trucks would have had it. As for the plastic retainers, they are just the most logical fastener for function and ease and speed of assembly.
I do not have one on my pickup. I painted the underside of the hood so that it looks fine without it and the sound of the engine is pleasing to me.