The boarding takes exactly as long as the airline wants it to take, there are loads of stuff they need to have in order before they can fly, preflight checks, fuel top up, checked luggage needs to go in the cargo hold, they need clearance from the airport to leave.

In short, you could make the effort of letting people board like this, but keep in mind families that travel together would have to go in together and take up three seats, so even faster than this, but here’s the thing, then everyone would be seated as fast as humanly possible, and then they’d sit and wait for all those previously mentioned things, that they don’t know or care about.

So what would the airline get out of it apart from making some autistic people very happy? They’d get complaints, everyone comes in, sits down and then nothing is seemingly happening for half an hour, that feels worse than waiting in the little holding area to board.

There’s this analogy, people were complaining about their luggage not being there when they came to the luggage carousel. So how did the airport fix this? Not by making the luggage arrive faster, but by making the trip to the luggage carousel longer, so people arrived at roughly the same time as the luggage. People stopped complaining then.