For those that seek knowledge
A historical remnant from the time when bottles were free blown using a blowpipe and pontil.
It makes the bottle less likely to topple over as the surface area is much smaller, enabling the manufacturer to have a larger margin of error in the production.
It consolidates sediment into a thicker ring at the bottom, reducing the amount of sediment poured into the glass.
It provides a small grip for a waiter or waitress to rest their thumb while pouring wine.
The small amount of space enables bottles to be stacked end to end easier.
It consumes volume of the bottle, thereby increasing the size of the overall bottle, making the bottle more attractive to the consumer.