I'm straight, so I thought about a situation in which two bisexual men were looking for a female.
On the one hand, two guys at once sounds awesome.
On the other hand, it also sounds like hell. You don't get to know them individually because they want to do the dating together. You have to get to know two people at once, at exactly the same rate, while they both get to know you (who are only one person) and then you know they're going to go home and talk about you behind your back. Even if it's in good terms. And so the relationship will keep going without you, and maybe even evolve without you. And the next date, you'll be where you left off, but the couple? They'll have talked about it and might have made decisions and suddenly there are decisions that were made without you and you need to catch up again.
It's hard dating and getting to know one person. I would never dream of trying to do it with two at once. And I would feel like I'm holding the candle (being a fifth wheel) and they're the one on a date, due to their history. They'll share jokes, they'll laugh.
Dating is awkward, you make yourself vulnerable. The upside is, the other side makes themselves vulnerable to. But if they're a couple, they have each other, they're stronger, and you're not. There is an obvious imbalance.
I would only give dating a couple a try if they allowed me to date them separately first until I got to know them.
Not to mention, are you going to stop dating and having sex with one another if your third isn't around? Because if you aren't that's another thing that's unfair. If I'm expected to always date both at once but they gate to date just the other, I'm obviously being treated differently, and it's easy for me to feel I'm being treated as less important. They each have the right to be there when I date their other partner. I don't have the right to be there when they date each other.
I think a lot of women will be scared off because they will feel they have to do most of the work and you'll get most of the benefits. I don't know exactly what the solution to that is, there are successful triads but I think I would suggest remembering all the relationships. When three people are together, there is a triad, but also three couples and three individuals. If you treat it as only one couple and one individual, you're being biased.
I'm not saying, be absolutely symmetrical, I'm saying, be fair. Any woman you date should be able to see you and treat you as the two individuals you are, not exclusively as a couple. The more you make it a "we" and "her", the harder it will be to incorporate her.
Think about it like atoms. Currently you are attached, and you think of yourself as a new unit. You need to break all the connexions first, and then get back together and create new connexions. You can't just add the new member to the existing relationship, you need to recreate the whole relationship to incorporate them. Your couple will remain, but if you look at all the connexions you see it's not a big connexion coming out of the previous relationship and linking the new individual to it. It's two connexions linking each of the two previous individuals to the new one.
Actually, I'll draw a quick sketch.
Here you go, this is what I mean:
I hope this helps you out. Good luck.