On Etsy and antiques retail websites, you can find glass bottles for sale that look like this:

Image: Vintage Arts

Image: Vintage Arts

These are handblown glass soda bottles, typically from the 1800s. As you can see, the bases are round, and that's not a manufacturing limitation, but a design decision. These bottles were purposely designed to not be able to stand.

Image: 86home

The reason is because at the time, bottles were all sealed with corks. Corks tend to dry out and shrink over time. With carbonated beverages, that's a problem; as the cork shrinks it becomes looser, and the built-up carbonation in the bottle can then cause the cork to pop right out, causing a major headache for the shipper or stockist.

Image: 86home

As a result, these bottles were designed to only ever be stored on their sides, which would keep liquid in constant contact with the cork, which would prevent the cork from drying out.

In 1892 American mechanical engineer William Painter invented the crown-style bottlecap we know today:

Image: KMJ, CC BY-SA 3.0

As Painter's invention gained popularity, round-bottom bottles went away, and at last soda bottles could stand.