What difference does 2 kilos make?

Losing 2 kilograms of bodyweight is attainable for most of us out there, but how exactly would this help your performance?
Which situation will really benefit from this change?

Long, steady climbs

Here’s where it’s at, if you hold the same
amount of wattage (let's say 200W) on a
5 kilometer climb with around 4% gradient
and you weigh in at 80kg as opposed to
82kg, you can save up to 30 seconds.