It has nothing to do with age.
Not true at all. If a middle aged or older man has hip/knee/back problems, he's going to have physical problems walking around malls, walking out on streets, or spending time on urban walking paths/in parks looking for approach options. Many middle aged or older men have orthopedic issues. A good portion of these middle aged or older men are married and aren't needed to find new women. Divorced or never married older men can often be dealing with orthopedic problems while needing to find new prospects. This is something more common than it was a few decades ago.
The same orthopedic problems can affect participation in night game, but are lesser factors into why older guys are not enthusiastic about night game. The bigger factors for older guys in night game are late nights/getting sleep and noise levels. I'd say it is common for a lot of men to burn out on nightlife venue approaching by late 20s/early 30s, which is usually before the onset of orthopedic issues.
IOIs are an issue as well.
The whole IOI environment has changed since everyone got a smartphone in their pocket and/or started using earbuds. Smartphones/earbuds have reduced the number of IOIs that men receive.
I noticed that by the early 2010s (my late 20s), I was receiving fewer IOIs than in the mid-2000s (my early 20s). The main change in those years was the gain in popularity of smartphones and earbuds.
In roughly my sophomore (2002-2003) or junior (2003-2004) years of college, the majority of females at my college gym did not use headphones/earbuds with an iPod (introduced 2001) or other MP3 playing device. In the 2002-2004 time period, only the absolute hottest women at that college gym were using headphones/earbuds to discourage approaches on the general gym floor. By the early 2010s, I noticed in my big city gym with mainly a 20s/30s post college crowd that the majority of women were using headphones/earbuds in the gym. That's a trend that has continued into the 2020s. It's very difficult to receive IOIs from women in the gym with headphones/earbuds. Only the absolute top tier men have a chance to break through headphones/earbuds and possibly receive an IOI. This is why the general gym floor is not a good place for approaching.
Headphones/earbuds have also made outdoor walking/hiking path and park approaching more challenging.
In nightlife venues, women are spending more time looking down at their phones than being present in the moment. That affects their ability to give IOIs too.
Millennial and Gen Z women have lost social skills to some degree since smartphones and earbuds have gotten popular.
The changes in the IOI environment are affecting both younger and middle aged men.