The elders which are among you I exhort, who am also an elder, and a witness of the sufferings of Christ, and also a partaker of the glory that shall be revealed: Feed the flock of God which is among you, taking the oversight thereof, not by constraint, but willingly; not for filthy lucre, but of a ready mind; Neither as being lords over God's heritage, but being ensamples to the flock. And when the chief Shepherd shall appear, ye shall receive a crown of glory that fadeth not away. (I Peter 5:1-4)
I spent 25 years in the military. When a commanding officer gives you an order, he doesn't say, "As a fellow fighter pilot and soldier, because I also serve our country, do XYZ". He says, "As your Commander...."
If Peter was the "Vicar of Christ", or the Elder of Elders, that would have been a great time to mention it. Something along the lines of, "Since Jesus Himself made me His Vicar, I charge you..."
It is kind of like Purgatory. In all those exhortations to behave well and give up sinning, one would expect SOMEONE to have written, "Don't you realize Purgatory awaits those Christians who sin? Don't you realize that with every sin, you build up temporal punishment and will burn for many hundreds of years more...unless you receive an indulgence from Peter?"
Or as redleghunter pointed out, if the Apostles believed in transubstantiation, then when they exhorted the Corinthians to treat the Lords Supper more seriously, wouldn't Paul have written, "The Lord's Supper is a perpetual sacrifice of Jesus, literally his own flesh and blood, being offered again and again in a timeless sacrifice by the priests I ordained!"?
Sometimes, what scripture DOESN'T say is important. And we reject transubstantiation, purgatory, and christian priests and the pope, not because we want to be different from the Catholic Church, but because the SCRIPTURE is different from the Catholic Church.
We are not trying to walk away from the Catholic Church, but to walk TO the Word of God. It just happens that those two are often the same thing...