The argument is the more inconvenience an option is (comparing to the alternative), less people will chose it. SDJ-ICN-SIN ticketed on KE/OZ wouldn't cost 60k yen extra, the cost of Airfare from A-C via B is not A-B + B-C, it might even be cheaper than TYO-SIN.
Yeah it would. Don't say "wouldn't" or "might". Don't guess. Don't make things up.
Price it out on Google Flights. You'll see what I mean!
Sendai airport is smaller than Halifax or Ottawa. Flight options are limited.... in fact, there's only one international flight tomorrow, and it isn't to Incheon. So your argument falls apart really fast.
You have to go to Tokyo if you want flight flexibility. That's just how it is in Tohoku.
In your example, the passenger would need to make 2 connections at Tokyo and Shinagawa.
Yeah, so what? You're
really hung up on the idea that connections are horrible monsters that are to be avoided at all costs, aren't you? What a weird attitude to take, especially in a train-heavy country like Japan, or England for that matter.
Changing trains takes a few minutes at either Hamamatsucho for the Monorail, or at Shinagawa. I've done both this year -- it's not onerous at all.
You'll spend more time walking through the Haneda terminal than you will waiting for that connection.