Why are some of the consecrated hosts reserved after the Mass?

While it would be possible to eat all of the bread that is consecrated during the Mass, some is usually kept in the tabernacle. The Body of Christ under the appearance of bread that is kept or “reserved” after the Mass is commonly referred to as the “Blessed Sacrament.” There are several pastoral reasons for reserving the Blessed Sacrament. First of all, it is used for distribution to the dying ( Viaticum), the sick, and those who legitimately cannot be present for the celebration of the Eucharist. Secondly, the Body of Christ in the form of bread is to be adored when it is exposed, as in the Rite of Eucharistic Exposition and Benediction, when it is carried in eucharistic processions, or when it is simply placed in the tabernacle, before which people pray privately. These devotions are based on the fact that Christ himself is present under the appearance of bread. Many holy people well known to American Catholics, such as St. John Neumann, St. Elizabeth Ann Seton, St. Katharine Drexel, and Blessed Damien of Molokai, practiced great personal devotion to Christ present in the Blessed Sacrament. In the Eastern Catholic Churches, devotion to the reserved Blessed Sacrament is practiced most directly at the Divine Liturgy of the Presanctified Gifts, offered on weekdays of Lent.