It is because we believe that the office of priest was done away with in the New Covenant. In the Old Covenant the priest performed the ritual sacrifices, were the only ones who could enter the Holy of Holies (at certain times), and were the go between (mediators) between the people of Israel and God.
In the new covenant Christ sacrifice was the final sacrifice for our sins and Christ is the only mediator between God and Man. And we, as a priesthood of believers, all have direct access to the throne of Grace and therefore do not need a “priest” to give us access to the grace of God.
We do however, believe that God calls and equips/gifts some to be pastors and teachers and leaders. They are not priest because their role is not to mediate between us and God by performing rituals and making sacrifices. Their job is to encourage and teach us to grow in faith and love as we seek after the Kingdom of God and His righteousness (edit to add) and oversee the day to day business of the (local) church.
And while, traditionally, the pastor and deacons/elders serve the Lord’s Supper in a gathering of the church and perform baptisms. It is also acceptable and in some cases encouraged for parents to have the Lord’s Supper at home with their family or for a Bible Study group to have the Lord’s supper with the participants in the group serving each other. Also, in many churches I’ve attended a parent or grandparent baptizes their children/grandchildren.
So Evangelical pastors are priest but not any more so than any other follower of Christ.