I think that Orwell includes the reactions of Benjamin and Mollie to bring forth the idea that if individuals do not get "turned on" to politics, in some form, politics will "turn on them." This is seen in how Mollie is only concerned with ribbons and sugar, the material pleasures that make her loyalty easy to appropriate and removing her voice in the process. Mollie is shown to be hopelessly manipulated by anyone and everyone. If anyone in the position of power showers her with ribbons and sugar, enabling her to remain pretty and her own interests being tended to, she can be bought. This results in a form of enslavement and her own voice never being authenticated or realized. Orwell is seeking to bring out the idea that those in the position of power benefit from a social order that can be easily distracted and appropriated. Social and political change that is meant to transform what is into what can be will never be realized if the price of individuals is so easy to pay for those in the position of power. Mollie's reaction to the revolution is meant to reflect such a reality.
Benjamin's case and his reaction to the revolution is a bit more complex because I think Orwell sees himself and other intellectuals in this light. Benjamin is fairly convinced that little, if anything, will change with the revolution. He never really signs off or validates the change in power. The only thing to which Benjamin is really loyal is Boxer. Yet, Orwell shows Benjamin to recognize his own silence actually emboldens in the position of power. Benjamin is not so cynical that he refuses to take action. He does take action. Yet, it is too late. Benjamin's reaction to the revolution is one of detachment. Yet, Orwell shows that such a reaction helps those in the position of power. No matter how detached and isolated one might wish to be, Orwell is suggesting that individuals have a clear obligation if they care about individuals in society to pay attention to political change, as it has some residual impact on those for whom individuals show affection and care. Benjamin recognizes all too late when Boxer is taken to the knacker's that political change has inevitable impact on who we are and in what we love in the modern setting.