What is the purpose for the "blog" section?

I've noticed some niche sites that have a silo structure have sub niches in the header menu to navigate the site, but they also have a "blog" section in the header menu.

Why not just include these posts with everything else instead of in this separate "blog" section?

If you build quality content in the blog section and share the useful content to social media, helps to drive some traffic to your money site. Also, Google increases your metrics due to some good traffic and quality of pages in each post in the blog. Also, you can build links internally with help of blog posts.

Info that doesn't necessarily fit into your "news" section are added here. It adds value to your site and keeps your visitors connected and engaged. It also a section where you can showcase your authority in a field you are in to.

It's for the content mate