The Scriptures read at Sunday Mass are not arbitrarily chosen by the pastor or parishioners. The Church has a three-year cycle of set readings
In this cycle, Year A centers on Matthew’s Gospel, Year B on Mark, and Year C on Luke. Passages from John are interspersed in the sequence of Gospels every year. Yesterday, we began Year B.
The Gospel passages read at weekday Masses, however, are the same every year. Since there are many more weekdays than Sundays, they cover a greater part of all four Gospels.
Generally speaking, the weekday Gospels include passages that are not read on Sundays.