Pair programming keeps us Agile because it shortens the feedback loop when reviewing code. This is feedback at its earliest and means that we're able to incorporate changes immediately, often nipping potential issues in the bud.

It's particularly potent when we follow the driver/navigator scenario, sometimes known as strong style pairing, the name attributed to a pair programming approach advocated by Llewellyn Falco. As per his presentation on https://www.slideshare.net/llewellynfalco/strong-style-pairing, he states that "For an idea to go from your head to the computer it must go through someone else’s hands."

This is cost-effective in the long run because it creates better quality software from the outset. Two sets of eyes are better than one and pairs are also more likely to keep each other honest; for example, due to peer pressure, we won't take shortcuts.

It's also an excellent way to skill or knowledge share, for instance, if one team member knows a particular part of the system well, or wants to coach a practice such as TDD.