Not only does it make sharing the piece on social more engaging, it gives the post new life in both Discover and Search.
The image is crucial for Google’s Discover feed on mobile (it makes up virtually the entire preview for the post) and can be presented as the thumbnail on both mobile/desktop in Search or within the page preview for Featured Snippets.
Image sizing is of course not everything, with the need to develop a unique, high-quality image that is relevant to the piece with Open Graph tags included.
Investing in a feature image for blog articles goes a long way. It makes a big difference.