Someone may ask "If devotional service is voluntary, then why do we have to follow so many rules? Rather, we should be allowed to do what we want.” But the rules and regulations are meant to provide guidelines by which we can learn to awaken our original desire to please the Lord. At present, that desire is covered by the desire to satisfy the material body. The rules and regulations help us change our habits and restore our original identity and desires. The presence of rules does not minimize the voluntary nature of devotional service. Krishna does not force us to follow them.
Lectures from a disciple Vol 1, Pg 328, 2nd Paragraph