What are the pros and cons of converting images to WebP by prepending i0.wp.com to the URL instead of using a plugin or manually converting them?

I've seen websites that use a function to replace the original image URL by adding i0.wp.com in front of https://, and I know they're not using Jetpack. They are literally using a custom function to achieve this. The final URL looks something like this: https://i0.wp.com/mydomain/wp-content/uploads/2024/02/banner-desktop.jpg