Yeah, this is my dynamic as well. My partner and I have been together for a decade and poly from the beginning. It’s not at all a secret, but people are so used to monogamy as a norm that they often just think our other partners are super close friends that hang out at our house a lot.
For some of us at some times in our lives, having a relationship with two people is less work. It requires much more communication, better scheduling, and much more attention to your partners’ feelings … but that might be a good investment of time anyhow, and often gets overlooked.
I find that having multiple partners helps me appreciate each partner much more, for themselves – it’s easy to mix up how much you love just having a partner and being loved, with how you actually feel about that person. Poly gives you the distance and contrast to see your partners clearly, and that can be really special.