While yes, computer labs with traditional desktop PCs would be more economically feasible, they simply aren't possible for public schools (at least the one I go to) today.
The point about writing is a good one that resonates with me. I grew up in the age where typewriters were dead, we would outline on paper, and then do drafts/final revisions in the computer lab. I can absolutely see why going straight to digital removes a lot of inefficiency... but I'm just still not convinced it couldn't be handled by shared machines. Having robust dedicated machines, even still in the form of a laptop, could be part of the classroom.
The well-off, computer-savvy parents will buy their kids a laptop and make sure you can log into the school system so that they get the same working environment at home, whether it's Google Classroom or anything else. That paper you started in class, show it to your parents, and keep working on it at home. It seems like a huge advantage if some kids can't do that.
Once you're giving all the kids a laptop, it doesn't really matter whether it's a Chromebook, it's just the cheapest way to do it, and it's good enough.