As Kepano said,
Style is a consistency problem
Having a style reduces the decision fatigue. We don’t have to check how to do every little thing every single time. We can just formulate a style guide and follow it, and make any alterations, if and when it proves necessary.
Just as Habits reduce the mental load for everyday tasks.
So we formulating a style guide to follow upon is very important, whether you are a company producing a product, or just a lone person writing your random thoughts to publish to digital garden. Having a style guide reduces too much cognitive load, and frees them up for things that need immediate attention.