Basically, in blogs like these you tend to elaborate on a point, investigating its nuances at length. It's like writing a newspaper column. You'll tend to include lots of text with long paragraphs that are not separated by subheadings.
They save time
But marketing and business blogs have a different requirement. Readers are often time poor, and are looking for useful key points and insights that they can implement immediately. So they want to be able to scan content easily. Therefore a chunky, punchy style is much more suitable.
They aid selling
And it has real benefits if you're using your blog to sell products and services. In that case you'll want to make your posts not just verbally compelling but visually so as well. Subheadings, along with bolded and italicized sections, bullet points and the like can give a blog a much more striking, lively appearance.
They improve clarity
Just as this style is appreciated by readers, it also has advantages from a writing perspective. If you use subheadings, they make you think about what each part of your post is really getting at. So they help you improve post clarity.
They suggest other ideas
Subheadings can also help generate other ideas. If you look at several subheadings, the list will often suggest related concepts. You can include those in the post. So subheadings can help you expand a short basic post into something longer and more substantial, without any fluff.