Why does a standard bottle (of wine, for example) contain 750 ml and not 1 litre or 1 pint?

Wine bottles vary in size around the world (and even more so over time), but what is called a standard bottle in the US used to have a volume of one-fifth of a US gallon, or 757 ml. In the UK it was one-sixth of an imperial gallon, or 768 ml, more or less. Standardisation for international commerce during the 20th century led to the adoption of 750 ml as the standard wine bottle.

https://en.wikipedia.org/wiki/Wine_bottle
https://en.wikipedia.org/wiki/Fifth_(unit)