It sounds like, based upon the little you shared, that your partner and you have very different levels of sexual desire on a day-to-day basis. I would hypothesize that you experience sexual desire more frequently, maybe even sometimes out of nowhere? Not much probably distracts you from having sex once you have decided that is what you want. Your partner is not like you. Your partner may be a person that needs someone to “warm them up” before they are interested in having sex. Sex does not just randomly occur to your partner as a good idea.
So, the good news is that no one remains in one state of sexual desire for their entire life. Maybe your partner even ends up more like you, and wants it often and will initiate. Maybe (one day) you won’t want it as frequently and reflect more of your partner’s habits.
Another question I have is, does your partner know any of this? Let us be mindful that our significant others are not mind readers; they do not just magically know because we think they should. Have you told them how frustrating you find this? Have you discussed why they don't initiate sex? Have you communicated how important to your sexual relationship it is that someone initiate sex with you reciprocally?
I usually recommend that my couples discuss these things, whether in the office or at home. I also assign that they take turns initiating sex, so that neither partner feels pressure, but a collaboration. That said, if you are going to ask your partner to alternate initiating, you do not get to judge when, or how, the attempt is made. You can discuss it later for “fine-tuning”, but not to criticize.
I have a feeling that it isn’t that sex doesn’t matter to your partner. I could be wrong. Yet, what I typically see is that it matters differently. Sex and pleasure occur and are experienced differently. Try finding out what your partner’s thoughts and feelings around sex are. How does your partner experience desire? Sex requires ongoing, open communication from both sides to be successful. This is a good conversation to have towards building a solid foundation for a long term, mutually beneficial sex life over time.