They're really getting old, sadly. I've been to various old bars around Japan and the venerable Pit Inn jazz club in Shinjuku for a matinee gig. I must have been the youngest person in all of those places. It was always pleasant to chat with the proprietors and regulars about their history and practices (except the well-known silent one-armed bartender in Golden Gai). I guess other styles of bar are popular among younger people, including the more anonymous chain izakayas and wine bars.
One bar owner in Sasebo, Kyushu (JAZZ SPOT EASEL) said that, despite getting very few customers, he continues to open each evening because he "really doesn't want a patron to come and be disappointed to find this place closed". What a sentiment. He talked about how young people are leaving smaller cities for better opportunities, causing them to hollow out. After closing, he brought me to an amazing, tiny (5 or 6-seater), hidden 50-year-old bar in a cave-like bomb shelter run by an even older man, who had his own stories to share.
For these people, it's a passion that has become their daily life. An era is fading as they retire or pass on, without younger people to take up the mantles. As visitors, we'll get to experience it for a decade or two more at most, I think. Definitely worth experiencing if you travel Japan, easy to find with just Google Maps, and even better if you can speak some Japanese.