Because professionals don't wait around synchronously for local builds when they can do distributed builds async.
Many projects don't have cutting edge build systems.
I'm also not committing temporary code just to make the CI produce a build that I'll need to download. I'll build locally.
What you’re suggesting is certainly the ideal case, but there are lots of things that can happen between where you are and where you want to end up. Saying that somebody isn’t a professional developer just because they haven’t reached the ideal state yet is bullshit.
It’s also easy to go around telling other people what they are or aren’t when you haven’t had the responsibility of building these building blocks yourself. You’re the user of them, not the creator of them. Have some respect for the giants whose shoulders you’re standing upon.
While I often do finish other development related tasks during longer builds, it doesn't make sense to context switch to something completely different during a 1-2 minute delay. I will build dozens of times a day while testing or optimizing functionality, so this can really add up.
That said recent versions of clang + lld + fission result in <20 sec compile+link times even on a multi-gigabyte executable, so the need for mold is significantly lessened. Users that are currently using gold will see a dramatic improvement.
Do you not have automated unit and integration testing?
Do you not have code review and CI before code lands?
Do you not have distributed, cached, incremental builds?
Improving build time isn’t just about changing 30-minute builds to 30-second builds, but also about changing 30-second builds into 2-second builds.