What is the wisdom behind the sacrificial offering (hady) for the pilgrim performing Hajj al-Qiran and Hajj al-Tamattu'?

The Qaarin and the Mutamatti are both required to offer a sacrifice (Hadi). If one is unable to do so, they must fast for ten days: three during the Hajj and seven upon returning. This is because they benefit from having one of the two journeys waived. For this reason, a sacrifice is not required from those whose families are residents of the vicinity of al-Masjid al-Haram.