Ali, possibly because BF has been proven to lower risk of SIDS considerably to start with over the course of numerous studies (fsid.org.uk/breastfeeding) and that dummy use hasn't been conclusively proven to help, although there have been studies to say that it could possibly reduce risk (fsid.org.uk/dummies), although that wording isn't exactly robust!!
I have no information about when dummies started to be suggested to be used, but could it also be that the article was written before that changed? It must've been published well over a year ago.