Market forces.
Since the advent of budget airlines, people have voted with their wallets. This has pretty much forced most other airlines to reduce seat space. Gone are the days where a 36" seat pitch was normal.
Don't like it, complain to the airline. Or purchase an upgrade to business class.
But if I'm in front of you, reclining my seat, I'd rather you didn't complain to me.
You could try choosing an airline with more seat room. Ask at booking time what the seat pitch is.