The older I become the more I appreciate luxury, comfort, and quiet.
When I was younger it was cool to ride in a Corvette but now I have no interest in being that low to the ground! :)
In my 20s I used to stand in line for up to an hour waiting to gain admission into nightclubs, pay a crazy cover charge, getting my hand stamped, and read under a black light. It was overcrowded.
Consuming alcohol without giving any thought to potential hangovers was the norm. I suppose "immaturity" is really about only focusing on what one wants (right here and now).
When you get older you start to take the long view on a lot of things. You also want to avoid being in the "herd".
As for being the "old guy" in the nightclub I believe online dating is a Godsend for the over 40 & 50 age crowd. It's another option for meeting people and some of the sites cater to older age groups.
There's also singlescruise.com which offers cruises geared towards single people of various age ranges.
Meetup.com is a hobby/interest site where various groups meet once or twice a month to share common interest. They have everything from wine tasting, yoga, meditation, book clubs, writers, hiking, theatre goers, single social mixers, and so on. Not every group is filled with single people but if you do meet someone you are assured you have at least something in common and you get to know them gradually via attending the meetings.
Having said that I don't see anything wrong with occasionally going out to a nice hotel lounge or restaurant that features live music from (my era) and has a small dance floor. I can't see myself dancing to any Lil Wayne music. LOL!