For the past 12 years, my closest friends have always been a couple. Is anyone else a natural 3rd wheel?

Obviously things would be different if I wasn't single. But why do I keep gravitating towards being a 3rd wheel?

It's not necessarily a bad thing. However I find it strange.

I was friends with a couple for 10 years, then kind of drifted away from both of them at the same time.

However in the last 3 years I've become close with another couple, and have a close bond with each of them individually, and together.

What gives?