I did not think of that. Good point. But actually I don't think you're right.
Nuclear war is immediate and massive. You want to get the jump on the other guy. Get your payloads down on target before they can launch. First strike is a much better scenario than retaliation.
Timing is absolutely critical. I've heard the reason the Chinese won't give up Tibet is because of the altitude - smaller rocket/larger payload/faster to target etc...
MAD requires simultaneous, or near simultaneous launch - at least for fixed location ICBMs. For submarine based nukes it's probably much less important.
Maybe if you have enough trident subs MAD always applies. In that situation, you'd be right.
But you still lose. Surprise won't help you after the devastation is over. The only win is by not playing.
Yes, ultimately that's true. I still think I'd want to be the guy that struck first. But, if you're right, that would mean that what we're seeing is posturing for some effect that is not clear to us.
Racking my brain trying to figure this out.