Yes, the main benefit of WEBP is for lossless compression, it's reported to be about 25% better, though this would depend on the image. For lossy, there's no reason I can see to prefer it over JPEG.
But you don't have to add extensions to convert this crap. You do that to yourself. If you quit making your life hard it would be so much easier, but probably less complaining- so i guess that's the trade off.
You do have to handle it though, and rarely when you want to. You click on a jpg link in your browser and save it, but the CDN invisibly converted it to webp. Which the program you want to edit the image in doesn't support. I didn't ask for webp. I didn't try to make this difficult.