Some people become friends for life. At least for me, they were the people I became friends with during my formative years. From my teens and up until young adulthood. Looking back, we became friends due to shared interests (movies, books, music), hobbies, and just general chemistry. Other people, you become friends with due to some shared situation. School, work, place you live, the places you go/frequent, etc. Once…
Perhaps times have changed or my friends don't actually like me, but in my experience this hasn't been true since I was like 16. People are constantly busy or otherwise unwilling to go out and do stuff together. If it gets worse with age then the outlook is extremely grim...