Because Incomedia did not implemented it yet?

I have set this post as an IDEA post, maybe they can set this up for future releases.

Thanks for the IDEA!

Maybe this post helps a bit?

https://helpcenter.websitex5.com/pl/post/222759

I understand from that post that png is better for websites, due to size (loading speed)

Hi

PNG very old and big size. New web picture format WEBP and JPEG 2000. But JPEG 2000 now not support web browser.

Other WEBP support Google and SEO

yes png is old, but still mostly used bij many websites.
Anyway i set this post for IDEA post so hopefully it will be added.