I agree @Corsadrive As you said, most but not all. I have been friends with people for a short spell - 2 seasons, or 2 years, and sometimes longer, like 3 to 5 years... I have enjoyed it for a while, but most have not lasted.
Sometimes we simply just drifted apart after one of us moved out of the area, and a few times, they just drifted away from me, or I drifted away from them. I drifted away because I stopped feeling a connection with them anymore, and felt we didn't have a lot in common anymore. I have had several friends who started annoying me, by being too intense and clingy, (or they became rude and unkind,) I contacted them much less and hoped the friendship would fizzle out and come to a natural end. In the majority of cases it did, and the friend and I just lost contact.
In most of of the friendships, I believe they were done with the friendship too. (As they weren't bothered by me not bothering with them.) Only a couple have mithered and badgered me demanding to know why I have gone 'cold.'
I have had a couple of instances in the past when a friend has just stopped bothering with me. So obviously they were bored with me, or found I was too clingy or annoying. I don't know as they pretty much ghosted me. I don't know why as they never told me, but I have done it to people too, so I can't complain about it much really!
I do have 3 good friends in my life who I have known for a long time, and am still in contact with - one going back to when we were 5 or 6, one I have been friends with since we were in our early 20s, and the last one since we in our late 20s. (I am nearly 50 now.)
Like other posters though, I disagree about the friendships being real. They were at the time.