That is nonsense.
1. Airlines are a business. They aren't a charity. Like any other business they exist to make money. Calling them or their executives "greedy" is ridiculous. Their goal, the same as yours or mine, is to make more money. The airlines are in a market economy and competition keeps the balance between price and amenities.
2. The airline industry is not very profitable
. They don't make very much money compared to other industries.
3. It cost money to run an airline. They have to buy and maintain airplanes, pay for gas. Then their are pilots and flight attendents and baggage handlers and ground crew and so on... all of whom want to be paid for their work.
4. If they give all the passengers more space, that means fewer seats which means less money. They aren't going to run an airline that loses money.
4. Customers keep demanding lower ticket prices
. Airlines compete for your business by offering you ticket prices that are near or even below the cost of taking you from point A to point B.
5. Airlines do offer you more space if you are willing to pay more. This is completely fair
bigger seats cost them more. Most customers aren't willing to do this.
If you are too cheap to pay a fair price for a bigger airplane seat, than be happy with your cramped seat. If we get rid of cramped seats, the price of airline travel will go up for us all
I happen to like going to visit family in Florida and coming back for well under $300.