Is it normal i don't get my grandparents relationship

They have been married 46 years .But have been best friends for 60 years.They are so loud and silly like little kids and rarely do anything apart. They are always bantering laughing or doing it. They have these big fights about stupid stuff and then five minutes later they are hugging like nothing happened.I asked them why they stay together when Their relationship seems like a rollercoaster and my grandma cackled and said their is nobody else and my grandpa said rollercoasters are fun. and then they poured each other wine and started debating why young people asked such strange questions.