Another factor to consider is "attachment style." Some people are more motivated to enter into relationships relationships and are more comfortable in them, making them more stable..
Of course, attractiveness is one of the most important features to be involved in many romantic relationships. Social status, to my opinion, is less significant. Others are the nature (style) of personal energy and the necessity of charisma. But also depending on the will of the person - is he (she) willing to be involved or not.
It really depends in the social environment, in some societies there is an expectation for a single relationship, in others, there is more fluidity. In all societies, there is an attempt to regulate sexual and romantic behaviours.
Sometimes as an escape from certain realities people tend to get into relationships. However, there are people who get attracted to quickly but are reluctant to start a relationship. Social culture also plays a role in deciding about the number of relationships a person should have.
Many factors control romantic relationships, as personality type, attachment style, society culture, other's attractiveness, plus conscious and unconscious factors affected our personality since early years childhood.
Some of them are unattractive and some do not have a successful way of communication and some of them have failed experiences and some of them are prevented by religion and belief