Because that is what Christ taught John, John taught his disciples, as bishops in succession to present day.
Their writings confirm it.
Indeed the Protestant Eucharist is heretical, and profaning the Eucharist and Christ.
That is what Christ taught.You are either for him or agaibst Him.
You cannot make up your own doctrine,
That is what the pillar of truth the true church teaches with the certainty of the power to bind and lose.