Dickens himself worked as a common laborer in his youth when family fortunes plummeted, and although he hated this period in his life, it was to leave an indelible stamp upon his consciousness, marking his works with an understanding of and compassion for the fate of the common man. In addition to his social and political activism, Dickens was probably the greatest comic and sentimental writer of his time. His exaggerated characters and situations served as marvelous tools to milk his audience for broad laughs and calculated tears. Remember, Dickens was a newspaper writer, and most of his novels were published in serialized form to sell newspapers. This cropped his technique and style in certain ways - he created a tone and style to appeal to the masses, and he created cliffhanger endings at the end of his chapters in order to maximize reader interest in the next installment.
People write for many reasons.
With many of the greatest artists, their writing is an expression of a story that just has to get out of them and find its way to the page. Dickens never wrote for art, but for commerce. He was a professional writer, and he intentionally pandered to the public's taste for sentimental stories. When he wrote, he didn't think as much about what was good as what would sell. Writing with mass appeal is certainly no sin.