I can't speak for anyone else but I simply don't want to go clubbing anymore. I had very wild twenties but now I can't think of anything more bizarre than getting dressed up at the end of the day and paying loadsa money to do something that is going to hurt the next day. I have my husband so have no desire to mingle and impress others and if I do want to spend time with someone I like to actually be able to chat to them. Money is an issue, in my younger days I worked to pay for nights out, now I work to feed and clothe my children. Time is also an issue, I can't be laying in bed recovering the next morning when my children want to spend precious time with me. I expect if I was still single and/or childless I'd still go clubbing but for me, there are more important things.
Yeah, so it looks like I've reached middle age, lol.