JPEG-XL is based on the Google Pik proposal among other things and they were active in the spec'ing - there is no conspiracy here.
(Safari learned this lesson earlier when they got stuck being the only browser to support JPEG2000, and Microsoft with JPEG-XR)
I'm not aware that they've shown any interest in JXL, so "little" seems unnecessary.
Google, with AVIF
AV1 and AVIF is landing in all browsers. They get the AVIF support for free when they implement the AV1 decoder.
No, it isn't free. You have to implement the support for the AVIF container. This is why libavif exists.
Google is a major contributor to JXL.
AVIF, as an outgrowth of AV1, has support from every major browser publisher, with the possible exception of Microsoft (though they are a governing member of AOM) as they're the only one which isn't shipping AVIF support right now (and as of October): https://caniuse.com/?search=AVIF
another format that is limited to three channels or has bit depth limitations would not be similarly interesting
another format that is for example 50 % worse in lossless compression would not be interesting in this space
Camera with a lossy / lossless 12-bit, 14-bit JPEG XL would definitely be interesting for many photographers. Not everyone wants to be forced to do a complete post-processing with RAW. JPEG is to limited (8-bit only) and HEIF isn't much better, while not having much support (especially on the web) because of the patent situation.
Also good to know that Jpegli (a traditional jpeg codec within libjxl) allows for 16 bit input and output for '8-bit jpegs' and can deliver about ~12 bits of dynamics for the slowest gradients and ~10.5 bits for the usual photographs.
Jpegli improves existing jpeg images by about 8 % by doing decoding more precisely.
Jpegli allows for encoding jpeg images 30 % more efficiently by using JPEG XL adaptive quantization (by borrowing guetzli's variable dead zone trick), and the XYB colorspace from JPEG XL.
Together, you get about 35 % savings by using jpegli from the decoding + encoding improvements. Also, you get traditional JPEG that works with HDR.
Jpegli is predicted to be production ready in April or so, but can be benchmarked already.