The social work field is very similar to the teaching field in that success often rides on a lot of emotional stamina, a lot of time, and a lot of relationship building, and in the end, there is very little pay.
"Love" is a difficult characteristic to quantify when it comes to a profession. I would actually argue that social workers need to have a certain level of love for what they do, otherwise they will not last long in the profession. Simply put, they are not paid enough to just "put up with" the emotional challenges they witness and experience on a daily basis.
I have known a number of social workers who worked (or still work) in the field of child protective services. Most would describe their job as "heartbreaking" because they see some of the most horrific situations and conditions that American children are living in. I think if you were to ask any of these professionals if they "love" the children they work for, they would say, "yes, definitely" but it wouldn't necessarily be a personal love. It is more of a general, humanitarian type love. This is probably the best definition of the kind of love most social-workers possess. It simply isn't a field of work that draws glory seekers, success hounds, or those who desire wealth. Social work is a professional field made of humanitarians, who, because of their love for others in general, sacrifice time, energy and emotion on a job that will never make them rich or famous.