"Friends." I think it's necessary to put that word in quotation marks because a friend is not what these people turned out to be. They say in the case of friendships, quality trumps quantity, and I've never believed that to be more true. People become friends for any of a million and one different reasons, but the reason people remain friends comes down to one simple factor: support. Friendships are relationships based on a mutual level of support. The relationships obviously become more complex over time and other qualities get added to a list of qualities that keep the friendship strong.
In my personal experience, I've had my fair share of these "friends." They're people that I've started referring to as "toxic friends." These are people who come into your life at one point or another and leave you worse off than before you met them. It's kind of like they take away something from you without even trying. They take what they want and utilize every part of the friendship until there's nothing left to take. I've witnessed them in almost every stage of my life, and I don't believe they'll stop appearing anytime soon.
Friendship, just like any relationship, is a two-way street. If each person doesn't put in the same amount of effort, it will not work. It doesn't matter how long you've been friends, what you've been through together, or why you've remained friends for however long; it will not work unless you're both willing to keep the friendship. This makes friendship sound over-complicated, but it's truth, simple truth, as to why friendships sometimes do not work.
If a person constantly makes you question their actions and your trust in them, they should not be in your life. It took me a while to figure this one out. I had to keep reminding myself of what they're taking away by being in my life. Once they realized I had nothing else to give them, it became clear to them that there was nothing else for them in the relationship. People like that need to realize that friendships aren't about what you can get out of it. It's what you can learn from it and how it might change you for the better.
It's hard to cut someone out of your life who's always been there. But, any type of relationship that isn't equal and fair will not end well. It's not fair to ourselves to try and keep these fleeting friendships alive. Why would you want to salvage something that is doomed to fail? Ridding those toxic friends from your life will feel like the most freeing feeling.