Right—I suspect one factor is that we have/had a weaker and looser food-culture than many countries, which fact has been exploited by companies to wedge food (so, food sales) into more situations and parts of our day, badly eroding whatever weak norms there had been.

Way, way more stores having very late or even 24/7 hours than before has probably further disrupted any norms and culture we had about when & where to eat—not just for the shoppers who have those wares available more hours of the day, but I'm thinking especially of the workers—believe it or not, young'uns, but as recently as the early 2000s almost everything in the US but certain districts of major cities were shut down and dead by a reasonable hour.

Another, possibly minor factor: I have a suspicion we have more waking hours per day, on average, than Americans did 50 years ago. You can't eat (snack) when you're sleeping, even if food's available.