Because it is ! But not.........
We (primary/wife and I) can only offer some of what we've learned after being "sexual" since an early age and continue to be. Many moons
We feel it's important to understand that sexuality has a lot of different aspects to it. We also believe it's important for everyone to explore them all to be a complete sexual being. To know what's most important for them.
Sex can be curious, fun & playful, lustful & animalistic and intensely deep/spiritual. We feel none of them are wrong and none of them are less important than the other. (spiritually leaning people will definitely disagree here but this is our views).
We believe acknowledging all these aspects is critical to being balanced, satisfied & happy. Our natural sexuality is a big part of our humanity ! We feel strongly that those unable to embrace that will suffer - sometimes much - because of that.
I seems from your writing that you may be struggling to try to pigeon hole your sexuality into one specific box as being more important than the other. We have found that unproductive at best. We all go through different phases, different moods, different circumstances etc and if it involves sex, trying to pound a square peg in a round hole usually results in a lot of frustration & confusion. And often a broken peg
All we can suggest is that you acknowledge these different needs - all of them very real - and try to get on the same page with your partner. If everyone understands this nature of things and tries to reach out and connect to the other to sense the CURRENT mood/need etc you may find the whole deal is a lot less complicated.
Hell, you can even make up a calendar in advance <grin> ! Monday is "PLAYFUL", Tue is "Wild & Kinky", Wed we do Tantra, Thur is "Orgy Day" etc
Point being - it's all natural - all good. ENJOY it - don't let it become a burden !