And classical utilitarians are notoriously prone to making quick judgments when tradeoffs are concerned:)
Perhaps people walk over hot sand because they really want to go swimming in the sea and would suffer otherwise. If there was absolutely nothing that subjectively bothers you about the current state you're in, you would not act at all, so it's highly non-obvious that people are generally trading pleasure and suffering in their daily lives. Whenever we consciously make a trade involving pleasure, the counterfactual alternative always seems to include some suffering as well in the form of unfulfilled longings/cravings.
Having said that, you can always ask why suicide percentages are so low if negative utilitarian axiology is right, and that would be a good point. But there the negative utilitarians would reply that a massive life bias is to be expected for evolutionary reasons.
If there was absolutely nothing that subjectively bothers you about the current state you're in, you would not act at all
Why not? The obvious reply is that, even if there is nothing that bothers you about your current state, you might still be motivated to act in order to move to an even better state. In any case, your attempt to make sense of the example from a negative utilitarian framework simply doesn't do justice to what people take themselves to be doing in these situations. Just ask people around (not antecedently committed to a particular moral theory), and you'll see.
I've always been more of a theoretician, but it's important to try one's hand at practical problems from time to time. In that vein, I've decided to try three simultaneous experiments on major Less Wrong themes. I will aim to acquire something to protect, I will practice training a seed intelligence, and I will become more familiar with many consequences of evolutionary psychology.
In the spirit of efficiency I'll combine all these experiments into one:
She's never seen Star Wars or Doctor Who.
She's never seen David Attenborough or read J. L. Borges.
She's never had a philosophical debate.
She's never been skiing.
Never had sex, never been hugged or even been licked by a dog!
She has so much to look forwards to...
(Though she'll be very boring for several months yet!)