We don’t have a passionless, roommate-like marriage, but I wouldn’t call it particularly passionate either. My wife and I (married for 13 years, known each other for 25) are both rather even-keeled; neither of us have extreme highs or lows. That applies romantically as well- although we have great and frequent sex, I wouldn’t call it passionate. I’ve had passionate relationships in the past- the sex can be amazing, but I’ve found that “passion” often translates to “highly emotional” in the other, non-sexual aspects of a relationship. Let’s face it- passion takes energy, and career, kids, and maintaining a home and the lives of four people can sap one’s energy.
Often, we are like roommates. She’s at home during the day, maintains the house and takes the lead on shepherding the kids hither and yon. When I get home we all eat together, I help the kids with homework, we both clean up the place a bit, get the kids off to bed, pay bills, etc. It’s easy to allow yourself to drift into a place in the relationship where you’re both just working to maintain your lives. Often you have to make an effort to break out of the roommate structure.
We have what we feel is a fairly common married relationship- we love each other deeply, are eternally committed to each other, and enjoy romance on a level that works for us. It’s not passionate, but it’s perfect for us and neither of us would trade it for anything in the world.