Why you keep running into WebP
WebP is Google's image format, and it does its job well: at similar visual quality it produces files roughly 25–35% smaller than JPEG, supports transparency like PNG, and supports animation like GIF. That combination is why a large share of the web now serves it, and why the image you right-click and save is so often a .webp.
The friction is entirely downstream. Every current browser displays WebP, but plenty of desktop software, upload forms, document tools and print services still do not accept it — which is the problem this converter exists to solve.