I hope Apple could further increase the use of JPEG XL inside iOS, if they could recompress all the JPEG inside my Photo Album it would instantly saves a lot of space.

For those who dont know JPEG XL can losslessly compress JPEG with 10-20% reduction in size depending on images.

The conspiracy theorist in me says thats a low priority due to perverse incentives (namely selling more storage at a huge markup).

Another rationale is that the Apple ecosystems tends to not use JPEG by default anyway, right? It uses HEIC or something.

Yes but most of images are from Whatsapp messages. And they are JPEG.

Apple was always very frugal regarding memory and storage

From discussion https://boards.4chan.org/g/thread/99659945/jpeg-xl-won

Recent benchmarks (crushing JPEG, WebP, AVIF): https://cloudinary.com/blog/jpeg-xl-and-the-pareto-front