Happiness is used today in the sense of “contentment” or “satisfaction” with regard to a utility function. It stems from cringe-tier utilitarianism of the Englishman.
I got some attention from someone, therefore I am happy.
I got 100 likes on my latest Instagram post, therefore I am happy.
This is not happiness in the philosophical sense of the word, or at least it’s not how non-utilitarians understand it. Because our world is dominated by the US consumerist mindset, their definition of happiness (ie satisfying one’s utilities) has unfortunately become the main definition of happiness.