Here are some of the main reasons as to why people may choose to join a pressure group:
Some people may feel strongly about a particular issue and want to help get change or raise awareness. For example, Greenpeace operates to not only raise awareness of specific environmental issues, it also works to get change by sending petitions to politicians and businessmen/women and taking part in publicity stunts.
Another reason why someone may choose to join a Pressure Group is to be able to protest more effectively. The government is more likely to take notice of 100,000 people protesting than just one. An example of this would be the Make Poverty History campaign that took place in 2005 when the G8 summit was held in Scotland. An estimated 225,000 people took to the streets of Edinburgh from all different Pressure Groups to raise awareness and push for change on one specific issue. It attracted extensive media coverage.
Some people may join a pressure group to gain voluntary experience; groups such as Amnesty International take on volunteers to work in certain parts of the world that are heavily impoverished.