"I always wonder how people who can afford to fly at all, let alone in Business or First Class (even if upgraded)..."

Well, I'll provide one excuse: my travel tends to involve international trips to places that aren't on the tourist maps. Consequently, the journey to the airport often requires carrying heavy luggage through a long succession of buses and trains, up stairs and down stairs, sometimes in countries where there may not be a word for "air conditioning" in the dictionary. That's before the 18 hours in airports and airplanes begins. No matter how cleanly pressed I may have been in the morning when I left, I'm sure I've probably occasionally ended up as one of the antisocial stinkers that you're talking about. And I'm sorry.