What is the goal of requirements engineering, and why does it put so much weight on achieving consensus among stakeholders?

The goal is to know the relevant requirements, reach a consensus among stakeholders about them, document them to standards, and manage them — all to minimise the risk of delivering a system that doesn't meet the stakeholders' real needs.

Requirements engineering is described as a systematic and disciplined approach to specifying and managing requirements, with these goals: knowing the relevant requirements, achieving a consensus among the stakeholders about them, documenting them according to standards, and managing them systematically.

Why consensus is central, not optional: a system has many stakeholders — users, owners, operators, regulators, the dev team — and they frequently want different, conflicting things. If you simply collect everyone's wishes without reconciling them, you ship a system that satisfies no one and triggers expensive late changes. Consensus means the conflicts are surfaced and negotiated before the system is built, so there's a single agreed target. The whole point is risk reduction: understanding and documenting what people desire and need, then specifying and managing it, so you don't build the wrong thing.

Tip: RE is a human-centric discipline — its target is a satisfied stakeholder, not a technically elegant document. Consensus is how you make "satisfied" objective enough to build against.