Actually, it would be nice if we could retire old image formats. For example, if/when JPEG XL becomes universally supported, the WebP format will be entirely redundant (lower quality, worse compression, no progressive, and it's not even faster to decode) and AVIF could be retired too (comparable compression, but much slower, and much more bloated HEIF container).
But currently browsers are Katamari Damacy balls endlessly accumulating more and more code. How long can we keep just adding without removing anything?
I sure hope so, because they're absolutely not a waste of bytes. Unless you personally are planning on converting all existing use of those old codecs everywhere?
What you're suggesting is an archivist's nightmare.
Redundancy assumes that either the original still exists, the encoded copy was lossless, the original was JPEG (which can be losslessly upgraded to JPEG XL), or that the new lossless copy of the old lossy intermediate will outperform. In reality the vast majority of AVIF and WebP images are lossy without the original copy meaning such a change will either force worse overall efficiency to now be a lossless reproduction of a lossy image or generational loss each time a new format takes over.
Not to mention the breakage and work effort during such change periods.
But currently browsers are Katamari Damacy balls endlessly accumulating more and more code. How long can we keep just adding without removing anything?