1) using third party infrastructure creates more brittle dependencies
2) it shouldn't be needed. chrome people must be doing something wrong if it takes so long
3) even if you had infinitely fast computers you still have to organize a lot of dependencies to build something huge like chrome. that's also a problem
4) sometimes the common method to compile something doesn't work and "secret knowledge" is required. some want to pretend it's common sense, but others struggle when processes have changed just for the sake of being different.