It's all part of the image. Buffett gets a lot of miles out of the (authentic or not) aww-shucks folksy homespun image. He can do questionable deals and still not have his integrity questioned, and it's disarming in negotiations, in which, Buffett is as tough as they come.

A website is a marketing operation. BerkshireHathaway don't really need to do marketing because they're more a legal entity for the purpose of organising things efficiently rather than a business with customers.

Similar to the personal websites of scientists. They are generally a tour-de-force of content over style.

as far as we know, it could be written in emacs org mode.