Final answer:
Many rock groups in the 1970s dressed up to express their unique style, rebel against societal norms, and keep up with fashion trends.
Step-by-step explanation:
In the 1970s, many rock groups dressed up for various reasons. One reason was to express their unique style and create a distinct image for themselves. Another reason was to rebel against societal norms and challenge traditional expectations of how musicians should look. Lastly, some rock groups may have dressed up to keep up with fashion trends and appeal to their audience.