You're right. Everyone expects brands to have a blog that's being kept up to date with interesting content. It's integral as the voice of your business. But a blog for the sake of a blog is hardly any better than no blog at all.
Blogs and other written content are the cornerstones of successful content marketing, and it's easy to see why: businesses with blogs generate on average 67% more leads than those without. Blog posts can be one of the best ways to build a relationship with your audience, as you add value while showcasing your organisation's values and personality.
Hopefully, over time, this will result in new business, but sales shouldn't be the primary objective of your blog. This format should focus on helping your organisation become a thought leader that provides trusted advice and inspiration to an engaged audience.
There's also no denying that regular, unique content is a key Google ranking factor, and a driver for social media engagement.