Seems like a pretty arbitrary selection of films to me. There are certainly more violent/sleazy films out there. Why choose these ones? Who knows... but here is the list.
What is a "video nasty"?
"Video nasty" was a term coined in the United Kingdom in the 1980s that originally applied to a number of films distributed on video cassette that were criticized for their violent content by various religious organizations, in the press and by commentators such as Mary Whitehouse. While violence in cinema had been subject of censorship for many years, the lack of a regulatory system for video sales combined with the possibility of any film falling into children's hands led to new levels of concern. Many of these "video nasties" were low-budget horror films produced in Italy and the United States. The furore created by the moral crusade against video nasties led to the introduction of the UK's Video Recordings Act 1984 which imposed a stricter code of censorship on videos than was required for cinema release. Several major studio productions ended up being banned on video, falling afoul of legislation that was designed to control the distribution of video nasties."