Consensus takes time.  Sometimes it's not needed.  Executive decisions are made.  Or, in an emergency, there's not time for a full evaluation of all views and opinions.  But when there is time, and it's an essential decision (i.e. not just what color should the new rug be), better decisions can be made---with improved "buy-in" by those in the group.

"Buy-in" refers to the people in the group not just verbally but truly accepting the proposed solution/action.  Usually it's when each person is indeed getting something out of the action that is valuable to them personally.  Without true "buy-in" people may seem to agree but then go and just do the minimum, or nothing at all, in the implementation phase.  This particularly often occurs when majority vote occurs: the winners say "yay we won!"---but the losers in the vote go away grumbling and determined to still fight against the majority.  So it's worth struggling to get true consensus to get everyone on-board, with their legitimate objections addressed.