Why do we correct mistakes?

Portuguese is my first language. I've spent the past month and half in an English speaking country. It is being has been my second time surrounded by native speakers all the time. One of my favorites "teachers" are is the children. I learn a lot from them. I feel jealous by seeing them uttering complex and perfect sentences perfectly.

Today, my niece who is an native English native speaker invited me to play a game. TWhen, I asked: - "Which game?". She immediately corrected me: - "What game?". She is nine. My other nephews and nieces who are underbelow seven never correct me, but they try to speak Portuguese when I challenge them. They think it is funny. My nine-year-old niece also tries to speak Portuguese, but it doesn't seem she is having fun enjoys it.

When I thought about that, I realized that our ability to experience the new diminishes at the same proportion that our capacity to correct others increases. By becoming confident in about the "world" where they (I don't know what exactly should be here, but not "grew".  Maybe -know from childhood )grew, people become less confident in about different "worlds".