Yes, it's the chase to some degree, but also because I enjoy my wife's company in many other ways. My marriage has always been based on more than just sex -- or is that a surprise to anyone?
If I had partnered sex every night, with imagination, humor, variety, role-playing, etc., it would take a long time before I got tired of it.
To be clear, I've had sex averaging once every day for decades. It's PARTNERED sex that's been missing. I don't think my biological drive would drop just because it became partnered!