One thought I keep coming back to is the immense consequences of how our units of length, weight and volume were defined. Products are often sold with round numbers (1 liter, 0.5 liter, 1 kg, etc). If you could go back in time and fiddle with e.g. the definition of a pint, you'd see that reducing its volume would lead to people drinking less, until it's so small that people just order two pints.