Per 100g doesn't make it easy to compare a bag of chips to a can of soda.

Unless you carry around a food scale to measure out all your snacks, I fail to understand why 100g^-1 is useful.

I would however be interested in a pie chart that displays the calories from different macros. Then tic tac would be 100% sugar and you could compare to soda, also 100% sugar, or chips, which are maybe 65% fat and 5% protein and 30% carbs.

Per 100g helps people compare similar products. But is that the problem that needs solving? I don't really think so. The issue is that people binge an entire package of food and don't realize how many calories they're actually consuming. These people are not helped by being persuaded to binge a bag of chips with 5% fewer calories.

100g of popcorn is not the same as 100g of chips.

The biggest issue I see with per-100g is it can allow trans fats to fly under the radar by including slightly less than 0.5g per 100g. If the true portion size is 300g then it’s much harder to hide trans fats