If it's a 2 hour wait each way, then that's 4 hours. 4 hours is a significant fraction of a day trip. A very significant fraction.
I would absolutely liken this to the difference between flying and driving. I can fly from Newcastle to London in a little over an hour. Add on train to central london, and arriving at the airport a little early, this means I can be in London from Newcastle in around 2.5 hours, making for a longish, but doable day trip.
The driving time from Newcastle to London is about 4.5 hours. Still doable in a day, but means that I'd have much less time in London, and the whole experience would be much less enjoyable. If I have the means to fly, I'm gonna fly.
If that means that a friend who can't/won't fly doesn't get to come on this one trip (and remember, it's ONE trip, I wouldn't be dumping them as a friend forever) then I guess that's too bad. I'll hang out with them another day, or we'll do a more practical trip, or maybe we will drive down someday, but not this time.
I think that's perfectly understandable.