There are many reason why people play poker. Some play poker to meet other people. Many friends like to hang out and play cards, and many people become friends over the card table.
For others poker is an entertainment. A game, a very competitive game. Many enjoy this game because they can use their brains.
Another reason is for skill enhancement. Playing poker needs skills. Poker will help you to improve your judgment skills (reading people) and sharpen your logical and strategic skills (how to play your hand).
Of course, other play poker for the money. But, not everyone can make a lot of money from poker. Nevertheless, the desire to win more is definitely a reason to improve your poker skills.