I guess it may have been, at least in part, because of his onw experiences in childhood where he had, at times, suffered some real deprivation and the harsher side of urban industrial society and its (often suppressed and untold) effects on children stayed with him.  He felt children had stories that needed to be told and could not be told by them.

Also he wrote in a time where children (and women) had no real rights.  In fact the notion of "childhood" was entirely differnent to what it is today.  Children's suffering remained invisible and Dickens worked to render it very visible.

There are many examples of this in Dickens....perhaps the most famous being in Oliver Twist.  Can anyone name other examples?

M

1. Dickens' idea was that every "evil under the sun" could be combated with the help of education. He really believed that providing good education to the children people could solve many social problems. The considered that roots of all problems were ignorance of people, poor education, cruelty of adults etc. From this standpoint the children's matter in the Dickens novels should be considered in connection with education and upbringing.

2. Victorian Age was an epoch of the novel. Almost all  English writers of this historical period  focused their works on issues of formation and development of a protagonist. Bildungsroman or education novel flourished with their contributions and turned into a basic literary genre of the time which depicted how social atmosphere, family environment could influence on a person and shaped him/her during the life journey.

3. Dickens invented and elaborated the new literary method of viewing world through the eyes of children.

These are the basic points why I think Dickens centered his novels around children.