When we focus on agreement without really listening to one another first, we risk going for deals too soon. We go for a shortcut. Typically in a tit for tat-manner like in politics: "If I will give you this, you will give me that in return".
Everything becomes a tradeoff. Which means that problems get solved by redistributing resources. Instead of looking for the causes of the objections, we throw more money at the people who hold power by withdrawing consent and bringing everything to a halt.
Most times this doesn't address the root cause of the objection, it just trades it with something which is of value to the other person. It may be completely unrelated.
At some point we want to come to an agreement, just after we have gone through the objections. And they might take us to different and better solutions than "You get more budget for X if I get Y".