Though I've used this term in the past to refer to a specific type of relationship, I am thinking now of what it is like to have sexual and/or romantic friends.
It's a pretty common statistic that 1% of the population is Asexual. While that does end up being a lot of people, the majority of people I will interact with in my life will be sexual, and it is likely that they will also be romantic.
These may not be the best friends to have for me.
I am Asexual and Aromantic.
I have thought about this for a while, and I believe that while it truly depends on the individual person, the likelihood of someone being an intimate friend of mine is significantly diminished if they are sexual and/or romantic (especially both).
I need to be able to have conversations with people that deal with things other than sexual relationships, sex, gossip about relationships, gossip about sex, etc. A separate issue is that I often do not know how to engage others- I tend to ask about relationships and/or sex, because it's something others usually respond well to, or it's all I have in my memory-bank of previous conversation history with said person- I simply don't know what interests them other than other people + sex/romance.
I like being able to be around someone and not have to constantly analyze the situation and my actions, to make sure I'm not accidentally displaying anything that could be taken as sexual or romantic interest in my behavior. This is because, to many, friendship, politeness, or closeness of some sort is interpreted as romantic and/or sexual interest.
I like being able to spend time with people whose company I enjoy and not worrying about whether or not they have feelings for me, or want to sleep with me.
A lot of the time, becoming friends with someone who is sexual and romantic, I feel like I am constantly lying. While friendly behavior and/or treating someone else kindly because you are a kind person should not be considered a giant waving flag of consent/ sexual/romantic interest/advances, my behavior is often misunderstood as thus.
As a precaution, I started telling people when they first meet me that I can be a wonderful friend, but that they should never date me. This initially scared people off of the love-boat, so to speak, but it wasn't completely effective- many thought I was merely playing hard-to-get or that I was some sort of kind but heartless, loveless monster. In one case, someone who I may have had a wtfromantic relationship with considered me completely unavailable.
Throughout life, I have tended to make friends with intellectual interests or pursuits, categorizing myself as a bibliophile and nerd, and I have made a lot of friends that fit somewhere underneath the LGBT+/Queer umbrella-- usually, these people understand that, regardless of sexual or romantic inclination, others aren't automatically going to like them or want to date them.
I haven't sworn off becoming friends with others who are not queer or creative or intellectual- but it's becoming increasingly clear that I don't have lasting, close friendships with them. I simply cannot handle being around someone whose values I just don't relate to enough to care about. If someone focuses on romantic/sexual relationships and is constantly talking about them and working towards them, there's just not much there to engage me. When I get along very well with the individual person, our contact is usually sparse- while they are imbetween relationships, or on the rare occasions they are comfortable tearing themselves away from their significant other.
I am capable of spending time with couples, but I usually hate it. Most couples disgust me. Not because of anything in their relationship, but because of the dynamic they have concerning others while in that relationship. If I cannot enjoy my time with people because they are simply horrible to be around while near each other because they ignore everything else around them...well...I probably won't desire to be around them more than once. If you can treat others the way you normally treat them (alone/one on one) while around your significant other/partner/whatever, that's fine. And romantic affection around others is fine, to a degree. The main problem I have with couples is that they tend to act exclusively and treat others like shit simply because they are reveling in their own filth/lovemaking. Maybe it's just the peers I've encountered in most recent years, but perhaps not.
For the particular friendships/relationships I want, I usually have the best luck with people whose lives aren't dictated or strongly influenced by romantic or sexual pursuits.
I also hate the feeling of being deserted because of a romantic or sexual relationship or opportunity. I've done something like that to someone in the past and it is one of my greatest regrets. I also consider it one of the worst things I have ever done, especially because it went against my nature. I suppose that particular time of life was an opportunity to solidify my preexisting feelings and beliefs and to learn not to do something like that again.
I personally cannot handle being treated lightly. If I value someone very closely and I feel those feelings are reciprocated, I rely on the friendship for my emotional and psychological needs. Those are the people I feel have my back, and I theirs. They are the people I am closest to and who I trust most. And if one of those people were to suddenly devalue me (or treat me so that I felt devalued), the hurt associated with that is much greater than it would be for someone I was not as close to.
If I am becoming close to someone and beginning to let myself care a lot for someone and they begin to show signs that they are romantic and sexual to the point of letting that destroy or greatly interfere with their existing friendships, I retreat. I hate it, but I know I don't want to stick around in a relationship in which I feel neglected or unimportant. Simple as that.