TL;DR Male-female friendships are not based on equality; one side must always be providing more value to the other
Three scenarios recently occured in my life:
#1 My car broke down at 1 am while driving home late. I called up my buddy and asked him if he could help me out; he showed up 15 minutes later. Later that week I showed up to his house with a 6-pack as a thank you gift and he says "Nah don't worry about it, we can share these beers". Equal friendship
#2 One of my female friends tells me that she is sick and asks if I can pick up her prescription across town. I tell her that I can, pick it up and drop if off at her place. When I get there her female roommate answers the door and I give it to her. I text my friend "Hope you feel better. How come you didn't ask your roommate to pick it up?". To which she responds Oh, I didn't think to ask her. At this point I realized that I was an orbiter for this girl and I decided to cut her out of my life. This was over a month ago and I haven't heard from her since. I was the orbiter
#3 I met a girl through friends; she wasn't very attractive but was a a sports fan so we would hang out and watch games occasionally. One day she texts me saying she got free tickets and invited me to go with her and I was happy to go. We had a great time and afterwards when we were walking home she says So are you finally going to invite me up?. I was surprised because I always thought we had a platonic friendship so I said "Nah I like you as a friend". To which she replies: I bought these tickets and treated you out tonight because I like you. You shouldn't lead people on like this because it's not nice. She was the orbiter
Most girls have a couple guy 'friends' that they hang out with and will continue to have even if the girl gets a boyfriend. This is where the 80/20 rule applies: 80% of a girls male friends will be orbiters while the other 20% will be past or future fuck buddies.
As part of the Unofficial LTR TRP Checklist one of the check boxes is:
Does she have a lot of guy friends?
The fact is that if a girl has 2-3 guy friends you can safely assume that they are orbiters that she keeps around because they treat her nicely. However, if she has more than 10 guy 'friends' then it is safe to assume that she wouldn't mind fucking a couple of them.
So next time your plate/LTR/wife is hanging out with a guy friend; ask yourself which one is the orbiter?