Passion can mean different things. Such passion may not be related to romance, but may also be about a passion for a shared interest or for one's children. Some level of deep connection and interest is needed to keep a relationship functional in the long term. A lack of passion at any level creates distance and leads to disinterest in the relationship.
IF you don't have passion and emotional connection in a marriage people will go out and find it else where. This doesn't mean that infidelity will be rampant but there will be a definite separation/ gap between the two individuals. Without passion it is hard to maintain the emotional bound in a marriage and that will cause issues later in the marriage whether that be infidelity or seclusion from each other.
I believe passion is extremely important in a marriage. I believe passion is the precursor that leads married people to form the deep bonds that allow them to become friends and life long partners. Without passion, I do not believe a marriage will be capable of lasting more than a couple of years.
I definitely believe that passion is important in a marriage. If a marriage does not have any type of passion, then it will most likely fail. I think it is important that couples in a marriage have some kind of strong feeling towards the relationship. If they don't, then there is no way it will succeed.
I believe passion is an important thing in a marriage, but it is only one part of many. Relationships take a lot of care and time and understanding. Many people are not capable of caring about another person enough to make a relationship work. Passion is important, but not the only ingredient.