imho loneliness is a systemic problem caused by a lack of understanding of what a friend really is. To demonstrate this, if you walked around and asked random people, or people you know, what a friend is, what is the odds they will answer correctly?
An acquaintance is someone you see in passing and have had a few conversations with. You know a bit about them, and hopefully enjoy their presence. Facebook, as far as I can tell, encourages building networks of acquaintances.
A friend, on the other hand, is an acquaintance you've gotten to know, but it turns out both of you want to one-on-one spend some time together. Catching up from time to time, or just hanging out. Whatever it is, both enjoy each other's presence enough to hang out outside of parties or meetups or whatever it may be. This usually comes from finding common hobbies but can be found through other methods. Sometimes I just like hanging out and watching a movie with people. Everyone has their preferences.
imho this is where American (and possibly Western) culture is failing atm. Many people like the acquaintances they know, but are unaware they can ask to hang out and spend more time together. It doesn't come up as a valid option for many people.
From there, there is degrees of friendship. Is it once or twice a year catching up, or is it someone you want to hang out with once or twice a month? This is often how circles of friends are created. When someone knows multiple people they want to hang out with once a month or less, it becomes easier to create group get togethers. I host movie nights, but go to gaming nights with people. It turns into that sort of thing.
At the end of the day, to have friends, you have to be a friend; you have to take that step of asking people to hang out or catch up. You have to be proactive. Otherwise, how will they know you like their presence? In a world full of people who do not know they can pull people into their social world, the few who do have an easy time choosing their friends and setting up their friend networks.
Not being lonely is important. Loneliness is the single largest precursor to depression. For many knowing how to gain friends is enough to curb or even remove their depression. For others there are other causes, which is why depression is such a complex subject.
Now you know what it is and how to do it. Now you have no excuse. Go make some friends! ^_^