Caro, flying to a meeting, I want to dress business appropriate just in case my bag gets lost. Even if I am taking a carry on. Recent trip, they made everyone check their carry on bags - not even gate check. Even if you carry on, there's the potential for flight delays, leaving zero time to change before the meeting. Or maybe you run into colleagues while you are checking in to the hotel. Then there is always the unfortunate baggage incident, as in, you accidentally pack a liquid or hot flat iron or whatever and you pull out your intended outfit -- and it's ruined. Or maybe you forgot to pack the right underwear or belt.
So yes I can give a long list of reasons to dress business appropriate on the way there. The way home is a different story, but often on my trips I wind up sharing a cab with a coworker to the airport, or otherwise running into a coworker at checkout.
Also - if you are dressed business road warrior style, other fellow such types chat you up in the airport lounge, or on the flight. This can be a disadvantage if you just want quiet downtime or to work on the flight. But I've made some great connections this way. And I am a social flyer -- I don't mind whiling away the airport/flight chatting with people who are equally open to chatting.
Then there's the whole generational thing. My mom raised me to dress up for air flight. I cannot shake that, I've tried. It's deeply ingrained.
The outfit you describe sounds quite lovely to me, and I have worn similar myself. My personal version right now is VC tube skirt plus comfy shirt.
What I can't mentally/emotionally jump over -- even for personal travel -- is wearing running sneakers, sweats, sweatshirt. I.e., gear. No matter how practical and comfortable, even if it was a 14 hour flight!! argh!! -- because of the generational messages that I grew up with. My mom's dictate to "dress up when flying" - I just can't shake that. I have tried.