The main point of conditioning in Brave New World is control. By conditioning people, the government is able to control how people feel and behave. Once that is accomplished, it makes governing and ruling over that population that much easier.
In the story, people are conditioned to like certain things and certain environments. For example, coal miners are conditioned to like dark, hot, claustrophobic environments. That means they love going to work each day. Happy workers are workers that are not likely to go on strike or be lazy workers. It's the same with every member of the Brave New World society. They are conditioned to behave in certain ways, and their conditioning is supplemented with Soma. Everybody is basically conditioned and encouraged to be happy all of the time. Happy people are pliable people and not likely to bother the government with demands for change.