If this were the case, the air would not keep increasing relative to bag size. Leaving all that aside, the crisps I bought as a child came in bags with nowhere

If this were the case, the air would not keep increasing relative to bag size. Leaving all that aside, the crisps I bought as a child came in bags with nowhere near this amount of "required" extra space. This is quite simply a deceptive marketing tactic to make you be at peace with getting less for more (or the same, best-case).