Most of the people that I know never use Instance Finder to find group members. They build the group from kin members, alliance members, friends list and sometimes glff. Once the group is complete, Instance Finder is invoked to start the instance.
This situation occurs in all games. People prefer to play with and group with folks that they know or friends not with strangers.
It is common problem in real life. Do not know any one. Do not have any friends. How do you get people to do stuff with you?
Unless stated otherwise, all content in this post is My Personal Opinion.