People are busy and can’t accommodate random pop-ins all the time. That is also a nightmare for certain personality types, and is often considered quite rude.

My dad is in his early 70s and still regularly gets together with people from all eras of his life, going all the way back to high school. Old neighbors, former co-workers and employees, and various others he met along the way. Unlike a lot of retirees, he has a rich social life and a packed calendar with dozens of close friends. This was all due to him regularly reaching out and scheduling a meal or activity, or just time to chat, over the course of his life. Friendships don’t just spontaneously last decades, they take effort, especially as people go through different stages of life.