It definitely shows trust issues when people are uncomfortable with this, it does seem quite common though. One of my girlfriend's friends is her ex-boyfriend, they were very serious and together for 5 years but it ended 6 years ago now (it was 3 years when we started dating). They gradually just stopped feeling romantic with each other. She goes to trim buds for him (he's a grower) for 2 months every year, along with various other people. He comes to visit her/us too, once a year. He stays at her house. I have no worries at all. He's been in her life a lot longer than I have. If when I met him there seemed to be something going on between them I would feel differently, but I have never detected the slightest hint that they still have any feelings beyond a platonic love for each other. Also she never makes me feel less important to her than him or anyone else. If I made it a problem, it would be a problem because she would feel restricted and disrespected and untrusted, and those things would be true. I have respect for her, so I give her the benefit of the doubt and trust her implicitly. If she gave me any reason not to, I wouldn't. It's a case-by-case basis. She has some other good male friends who I haven't met who are scattered around the country... if she lived in the same place as any of them they'd hang out and be close too. I have male and female friends, and so does she.
My ex also had some male friends, she even very briefly dated one of our mutual friends shortly before we started dating. Never bothered me because I never got a sense that she would do anything with any of them, I trusted her too. She didn't trust me as much, she also would get really angry if me or anyone else mentioned any of my exes, which was weird and unfair to me since I never gave her any reason to not trust me either. It made me feel disrespected, and in fact it was disrespectful.
I dont know any males who are "good" friends with any females that they wouldn't shag given the opportunity. All I ask is that my chick acknowledges that those guys are hanging around for a reason. After many years and proving to her that guy who isn't attracted to her at all in her mind will drop everything to bang given the opportunity she finally understands lol
Not always the case at all. I've had various woman friends I've never wanted to bang, including one of my late dearest friends in the world (RIP Erin

), never had the slightest desire to have sex with her, I never would have gone there. I have even found some of them attractive, but it just wasn't where I wanted to go with them.