The apparent answer to that question has everything to do with the National Rifle Association (NRA). Many consider the NRA to be one of the most influential political lobbies in the U.S. because of its ability to consistently deliver large numbers of votes in elections, as well as its record of campaign contributions and activities in lobbying for gun and hunting rights. Members of congress have ranked the NRA as the most powerful lobbying organization in the country several years in a row.
The more in-depth thinking will lead you to many of the society problems and the firearm industry in US. Michael Moore's documentary film "Bowling For Columbine" had some meaningful analysis on this. It is recommended. "Columbine" refers to the notorious Columbine High School massacre in yr 1999, in which 12 students and a teacher were killed by two teenagers.
Charlton Heston (NRA former president) giving his well-known and much parodied speech, when responding to those in favor of gun control, he proclaimed they would have to pry it "from my cold, dead hands".