The reason is this is what they look like before air is blown in. It would be much harder to get air to inflate the plastic asymmetrically.

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The reason is this is what they look like before air is blown in. It would be much harder to get air to inflate the plastic asymmetrically.

Damn. Now I want that bottle.
From my experience, stick it in the dishwasher, and it may revert to that.
This particular design would be harder to stack. But, that could be solved with a post sticking up from the center.
In spite of the claim, it would not "change a lot". It's a small change, little more than a marketing gimmick. It's not a big problem.
What would change a lot is not buying single-use disposable plastic bottles.

Milk cartons
Probably because that would be more useful for bongs
I like the way you think
Because it requires asymmetrical mechanical force at the end, while symmetrical force is required produce what's there already. Rotation would be required, so the short side would thicken or the long side would thin. Much easier and less error prone to use a set of round dies in a tube running straight.
I just made all that up with common sense.