I'm sorry, but JPEG compression is extremely noticable especially with non-photographic material such as web graphics. The compression is lossy by nature, and predictably introduces noticeable artifacts. WebP on the other hand has support for lossless encoding.

It's simply not the same thing. If I opened my file browser one day and saw that all of my FLACs had been converted to MP3, I would go on a murder spree.