If they produce content for the sake of conversions, does it really matter to them if you hit back as soon as you see the popup? You've self-selected to indicate you aren't interested in doing business with them based on their popup practices.
From their perspective, this could be a bonus. Not that server resources are that scarce, but sales resources can be. Now they don't have to have someone call you, don't have you in their denominator lowering their conversion-to-sales rate, etc.
Perhaps it's just a way for both reader and publisher to see if they're a match.
After considering your comment, I still think my original point stands. Instead of thinking about the product being sold, think of it like qualifying a lead based on their receptiveness to your advertising.
It would need to be tested whether that would be more highly correlated with conversions / profits, but I'd probably consider someone who is receptive to my advertising as a higher priority lead than someone who is interested primarily in my content.