Why not put white wine in a square jar?

This reason is related to the cost of making cans.

You should know from the TV introduction that the ceramic jar is made on a rotating board. Put clay on it, rotate it, and you can make round pottery by hand.

And you can't use this method when making a square.

Relatively speaking, the time cost is high and the labor cost is high. The round ones may be hundreds a day, and the producers may only have a few a day.

So, if you are a winery owner, you will also choose a round jar instead of a square one.