I think its more that HTTP/3 only really gives marginal gains for most people.
Just as python3 had almost nothing for programmer over python2, apart from print needing brackets. Sure it was technically better, and allowed for future gains, but in practice, for the end user, there was no real reason to adopt it.
For devs outside of FAANG, there is no real reason to learn how to setup and implement http3
I’d go even further and say that HTTP/3 gives almost no gains for the average person using a high speed wired or wireless internet connection at a fixed location (or changing locations infrequently).
However, for high latency mobile connections while roaming and continuously using the internet, it’s quite an optimisation.
I wouldn’t expect even the vast majority of devs in FAANG to care. It should purely be an infrastructural change that has no impact on application semantics.
Just as python3 had almost nothing for programmer over python2, apart from print needing brackets. Sure it was technically better, and allowed for future gains, but in practice, for the end user, there was no real reason to adopt it.
For devs outside of FAANG, there is no real reason to learn how to setup and implement http3