There's nothing illegal about "replica" or "inspired by" handbags (as long as they don't use the designer's name/logos or try to pass them off as "AAA replicas" or "mirror images" they aren't breaking any laws). Walk into your local Target store & take a look at that newest releases. More than half of them are "inspired by" designer bags. I don't think they should use the term "knockoff" because to some, that implies counterfeit, but all they really are is inspired by designs.
Although I personally wouldn't carry one, I'd much rather see some one carrying one of these bags then an illegally produced, counterfeit handbag. For some people who like the look of Chanel, LV or Balenciaga, but cannot afford it, these bags are a much better choice than the bags sold on street corners, iOffer or even ebay.