Why is everyone negative?

I have noticed that most people like to mostly add negative comments to a conversation. For example - "Do you know what I hate...", or "This line is taking so long" or "I'm so tired of that". Why can't people say "I wouldn't prefer that" or "this line is long, but I'm happy to be getting this done and they are probably just backed up". Why do we feel so entitled? Americans are twice as rich as they were in the 70's and they rank no happier b/c of it, Japan is 6 times as rich as in the 50's and they are not any happier either. If you own a car you are richer than 84% of the world's population. We live in the U.S. and even the poor are so much richer than everyone else, but still I hear how bad things are nowadays or "where this country is headed". Studies prove most of the time rich successful people are no happier than the average person, you choose to be happy. I am trying to reduce negativity from my life, but 98% of people are just ingrained in a this could be better mindset. Why does so much of our thought revolve around negativity instead or positivity and great-fullness?