I fly to NL twice a year :) I fly mostly to Asia for clients. But I would do that twice a year by train if it were cheaper as that's (usually) not for business.
And yes, I agree they should add it on. I am not bothered with paying a bit more and making it more sustainable, so I try to convince clients to do more via video conferencing, but it is just not as good. I suffer from terrible tinnitus and I found that a lot of (men) suffer from that as well but don't talk about it (shame?) so in conference calls often just no-one can understand anything and politeness/shame prevents anyone (but me) from saying anything about it. Face to face that issue is just not there.
Edit: also I would Find it a better idea if the gov subsidizes the NS like they used to; you want cars of the streets and people travel less by air; make trains really really cheap. Inside NL it's often cheaper (and definitely more convenient) to take the car as well. To me that makes no sense really. I take the train usually in NL because I don't have a car there, but everyone I know just takes their car everywhere unless they live in the center of Amsterdam and travel inside Amsterdam.
Edit:
> I can understand why someone would do that, but it is affordable only because aviation is mostly untaxed and very inexpensive compared to any other transportation modes.
I understand this point that yes, that is not fair. And I understand it is not a viable model if I would just fly where I work (which I don't; I work 90% from home) and I know others do though. But the non sustainable model comes from the fact there are too many emissions which are not covered; as a consumer, why would I care, in any other way but that, about how these prices are formed? I see they are (a lot cheaper), so if I cover the emissions, they are still cheaper. So it's far better than taking the train if you look at it like that. And it does not seem to change soon either so seems quite sustainable too.