Packets of…. what?
I definitely do look at serving sizes on food packaging. I’m trying to control my caloric intake, and because manufacturers are deeply inconsistent in how they list them, you can’t just look at the calorie number. You HAVE to look at serving size. The same size box of something will sometimes use wildly different serving sizes, and thus one looks healthier…but has in fact chose a serving size that is less than half of the other.
But if you’re asking if serving size tells me how much I need? No, not really. I find most manufacturers list serving sizes for the purpose of driving down the calorie number. If I really served myself one ‘serving’ it would be inadequate.