In my experience, students do not like to work in groups because they feel one or two people end up doing most of the work while the others sit back and do not do much. Some students do not see the value in working together, they would rather work independently. For one of my classes, I have students take a group test. Often the students are reluctant about this at first. When they take the test with partners they are able to talk out their answers. Some students say they learned mmore from working together than they did from the lecture. Other students did not like the group could not consent on an answer. Once the students get their test scores back I have the write a paper together and they talk about the pros and cons of taking a test together. I think it is important to do this because it teaches students to work together.