This perspective is so mind-blowing to me. I'm Western European, and all of my male friends have female friends, all of my female friends have male friends. That's what's normal to me. When I hear people say things like "friendship between men and women always has sexual tension," that's what sounds "not normal" to me.
I guess it has a lot to do with cultural norms and gender roles.
I have no idea how common these types of situations are elsewhere.
I'm from central/eastern Europe, and I feel a little bit of WEIRD bias [https://en.m.wikipedia.org/wiki/Psychology#WEIRD_bias] in many opinions presented here.
I'm not saying it's wrong. I'm just finding myself more and more blocked when it comes to discussing such topics.
Your friends have friends of different sex - I get it, but for how long we would have to debate here to check if there really is no sexual tension there. Where does relationships come from then in those groups? None of those friends become pairs/partners? There are no ex-lovers who after 10-20 years are coming back together from the "friendship phase". Etc.
On the other hand, I never said that there is only sexual tension. Just that it's hard for me to imagine a world where it's not important.
And some I hope to someday fool around with!
It's not simple, but the vast majority of the time it is not a problem either. The real problem comes from jealous partners, and I personally would never date someone who is so jealous that they cause problems with my existing friendships.
For example, I'm friends with most of my exes. We're all in new relationships. I sometimes go out for dinner with one of them to catch up on life and talk. There is no sexual tension at all, because we are in different relationships, so sex is not something we even think about!
If we were both single and an ex would call me and ask if I'm alone tonight and if she can drop by and watch a movie, then that would be a completely different situation, and there very likely would be sexual tension. But this is highly situational and has more to do with circumstances than with the people involved.
Just because I had sex with a person in the past or might in the future or could in theory does not mean that there is constant sexual tension between us.
Lot's of friendships start with brief dating/hookup that doesn't lead anywhere romantically. And frequently major relationships leave bonds that persist after the relationship ends. I'd be hard pressed to think of ANYONE I know who does not have at least one friendship like that (I'm early 40s).
If people agree that they like each other, then there is sexual tension, because they both instigate that sexual tension.
If they aren't attracted to each other, then there's obviously no chance of sexual tension in the first place.
For some people I see on the Internet, sex seems to be an overwhelming factor in their lives, and they see all relationships through that lens, but I've never observed that in real life. Sex and romantic relationships are just one part of people's lives, and most friendships are never perceived through that lens.