the belief that people of different sexes couldn’t be friends without someone wanting sex (regardless of reciprocation) was pervasive when I was a young person and I expect people have only grown more attached to the illusion as time proceeds, so (at least in amerikkka) there’s also this social pressure to congregate with people of the same sex when “hanging out with friends”, which probably amplifies the effect

I am from europe and gen z and this was the case when I was young too. Hell even nowdays some people still believe that. I was called gay for simplying having female friends (I mean I am, but still a 10-year old doesnt really know that yet).