Many people consider being in a “throuple” to be a positive experience, although it isn’t for everyone. There aren’t “advantages” in the sense that people who aren’t interested should be encouraged to try it, for the sake of those advantages, but there are benefits for people who want to be in a threesome. Avoiding your romantic or sexual interests just because they have been considered taboo in the past is a surefire way to put stress on any relationship you do have, so people who have an interest in threesome dating should find a way to make it work for their situation.