It’s really simple, when a human sees another human speaking a language, right in their face, we learn languages naturally. For practical reasons this is typically very difficult to arrange for two adults, especially for the amount of clock time required. Now you can see beautiful humans speaking right in your face, 24/7, 365.
Many people dream of going to another country to learn a language, even there the physical and social limitations remain. If you do go, know the language already and start making friends from the beginning or maybe some new friends in your home country!