Some will, you just have to pay an extra fee when you buy the ticket. It is ridiculous.
I understand airlines are very feast or famine and often operate on very thin margins, but at this point I’m willing to pay a little more for the experience to not be so categorically and consistently miserable
Otherwise I find everything ok. The flights are fine -- packed but it is what it is there's high demand. I could do with/without the food if it reduced the price, I can pack my own. But otherwise I find them fine.
What makes air travel miserable for you?