They’re also incentivized to keep the same size packaging (both for logistical and public perveption reasons) and ship less product in those packages. People are willing to pay $6 for a big bag of chips, despite the big bag weighing 150g less than the normal bag 5 years ago.
They don’t get paid by the gram, they get paid by the bag. A bigger bag looks more impressive, and thus can be sold for more. Same for those tall skinny beverage cans. They look bigger than the regular cans, but are actually 25ml smaller, and yet go for a similar price.
This will continue until the price per gram is what people look for (emphasis on this at the point of sale would help), or the mass of each product is standardized. 50g, 100g, 200g, 350g, 500g, 750g, and whole kg sizes only, none of this 489g nonsense.
You underestimate how little people think when purchasing things. None of this would be a problem if everyone looked at the price per 100g first, but ooo 3 $5… And then the size reduction usually goes alongside a packaging change, like jumbo or family size; “New look, same great taste!”. It’s all a distraction, out of sight, out of mind and all that.
Also, the 330ml cans are taller, and because of the square-cube law they only need to be a little skinnier to be smaller. They’re also not usually displayed next to the normal 355ml cans. Out of sight…
Also, who is going to laude a big corp product for a logistics change in the first place? I barely see anyone complaining about shrinkflation for packaging reasons as it is. I’d see a better slack fill level on one product and think, “This must be old stock” or “This is the last time we’ll get bags this dense”.