From Wiki , https://en.wikipedia.org/wiki/Usenet#Decline :
In 2008, Verizon Communications, Time Warner Cable and Sprint Nextel signed an agreement with Attorney General of New York Andrew Cuomo to shut down access to sources of child pornography. Time Warner Cable stopped offering access to Usenet. Verizon reduced its access to the "Big 8" hierarchies. Sprint stopped access to the alt.* hierarchies. AT&T stopped access to the alt.binaries.* hierarchies. Cuomo never specifically named Usenet in his anti-child pornography campaign. David DeJean of PC World said that some worry that the ISPs used Cuomo's campaign as an excuse to end portions of Usenet access, as it is costly for the Internet service providers and not in high demand by customers. In 2008 AOL, which no longer offered Usenet access, and the four providers that responded to the Cuomo campaign were the five largest Internet service providers in the United States; they had more than 50% of the U.S. ISP marketshare. On June 8, 2009, AT&T announced that it would no longer provide access to the Usenet service as of July 15, 2009.
AOL announced that it would discontinue its integrated Usenet service in early 2005, citing the growing popularity of weblogs, chat forums and on-line conferencing. The AOL community had a tremendous role in popularizing Usenet some 11 years earlier.
In August 2009, Verizon announced that it would discontinue access to Usenet on September 30, 2009. JANET(UK) announced it will discontinue Usenet service, effective July 31, 2010, citing Google Groups as an alternative. Microsoft announced that it would discontinue support for its public newsgroups (msnews.microsoft.com) from June 1, 2010, offering web forums as an alternative.
Primary reasons cited for the discontinuance of Usenet service by general ISPs include the decline in volume of actual readers due to competition from blogs, along with cost and liability concerns of increasing proportion of traffic devoted to file-sharing and spam on unused or discontinued groups.
Some ISPs did not include pressure from Attorney General of New York Andrew Cuomo's aggressive campaign against child pornography as one of their reasons for dropping Usenet feeds as part of their services. ISPs Cox and Atlantic Communications resisted the 2008 trend but both did eventually drop their respective Usenet feeds in 2010.