But why is it so clearly stated that we are all to be priests and offer spiritual sacrifices, and not that the bishops or deacons would offer sacrifice for someone else?
I don’t think there is anything especially explicit in the Bible. However, explicit mention of the Eucharist as the Christian sacrifice and of the celebration of the Eucharist being restrict to the bishop and his designates can be found in the Apostolic Fathers, such as Ignatius of Antioch’s
chapter 8Epistle to the Smyrnaeans,.
Probably the closest thing you are going to find in the Bible to the mention of a Christian ministerial priesthood is the mention of a Christian “altar” and “those who serve the tent” in Hebrews 10:17 and St Paul’s imperfect, triple comparison of the sacrificial worship of Israel, pagans and Christians in 1 Corinthians 10:18-21. Keep in mind that in the Bible the word “table” is sometimes synonymous with “altar.” (see Malachi 1:7,12) And, altars imply ministerial priests who serve them.
We know that the Jews engaged in sacrificial worship, where a Jewish priest would offer food offerings and/or drink offerings in cups in sacrifice on altars dedicated to God and, except in the case of whole burnt offerings, and those who wanted to be partners with God then partook of those sacrificial offerings. Pagans also engaged in sacrificial worship, where a pagan priest would offer food and/or drink offerings in cups in sacrifice on altars dedicated to idols and those who wanted to be partners with the idols then partook of those sacrificial offerings. See 1 Cor 10:27-29; Act 15:29, concerning such food sacrificed to idols.
Unless St Paul was comparing apples to oranges, Christians also engage in sacrificial worship. Since “the table of demons” and “the cup of demons” mentioned by St Paul in 1 Cor 10:20 in context probably refers to the sacrifices of real food and drink offered by pagan priests on altars dedicated to idols, “the table of the Lord” and “the cup of the Lord” mentioned by St Paul in the next verse (v. 21) in context probably refers to the sacrifices of real food and drink offered by Christian priests on altars dedicated to God, i.e., to the “the bread we break” and “the cup of blessing we bless,” which are participations in “the body of Christ” and “the blood of Christ,” at “the Lord’s Supper” at Church assemblies. (1 Cor 10:16; 11:17-34)