Popular or famous?
Can't answer for the rest, but I like them because I like my watches large due to the fact that I have a large wrist (read fat). I like my watch toolish and robust and perhaps even value for money. Panerai seems to fit the bill (at that time). I like the fact that it use to be limited in production numbers, hard to get, and a military secret. Ok maybe not the last one. I like the simple dial layout, minimalist in approach and easy to read at a glance. Sadly, all these are no longer true of the brand. As such, I no longer buy them new but rather preloved and only specific models. I still like the watches they make, but they are moving up the food chain. However there is a replacement in Tudor. They (Tudor) are currently at where Panerai was back in 1997/1998.