I was thinking about this as well.

In short, spending time alone could also have to do with being beat down by work. Long hours, lower pay, worse benefits. Statistically, America's lower class is getting poorer.

I have to think it's easier to get together with friends and family more when you have more free time and disposable income.

But even this speculation is a jump to conclusions. I am very wary of articles like this that are quick to assign cause.