Is this Image Optimization good for SEO?
Absolutely. Among many other signals used by Search Engines, one of the most important is the website loading speed. Having smaller in size, optimized images means the site will load faster and use less bandwidths. And Search Engines love that! :-)
Here's how Google puts it (read more here)
Images often account for most of the downloaded bytes on a page. As a result, optimizing images can often yield some of the largest byte savings and performance improvements: the fewer bytes the browser has to download, the less competition there is for the client's bandwidth and the faster the browser can download and render content on the screen.