Because God Said So every sunday.
The bottom line is we do all this the way we do it because God said so. We take His word for it. We take His word for it because He rose from the dead, and He safely handed on His words and deeds every Sunday at Mass since He rose. The Mass is the one thread through history that hands on a living tradition. The Mass is a golden chain, and the links of the chain are every Sunday since the Resurrection. The Sunday mass of the Catholic Church is the strongest living witness to the Resurrection there is.
The Mass is the golden chain and the links of the chain are every Sunday since the Resurrection.
Catholics would not go to church through centuries of persecutions if they did not believe that Jesus rose from the dead to raise us, and gave Himself to us under the form of bread to feed us. Based on the words of Jesus, we say Jesus is actually present once the priest says, “This IS my body.” Only Catholics say this. If it was not true, it would be an absurd thing to say. If the words and actions and truths in the Mass changed from Sunday to Sunday, the people would have exposed the lie. But God does not lie, and He protects His Church and His message down through the ages.
Someone may say, “OK, but there are people who go to Mass who don’t believe.” The answer is in the parable of the wheat and the weeds:
The Parable of the Weeds Among the Wheat.
He proposed another parable to them. “The kingdom of heaven may be likened to a man who sowed good seed in his field.
While everyone was asleep his enemy came and sowed weeds all through the wheat, and then went off.
When the crop grew and bore fruit, the weeds appeared as well.
The slaves of the householder came to him and said, ‘Master, did you not sow good seed in your field? Where have the weeds come from?’
He answered, ‘An enemy has done this.’ His slaves said to him, ‘Do you want us to go and pull them up?’
He replied, ‘No, if you pull up the weeds you might uproot the wheat along with them.
Let them grow together until harvest; then at harvest time I will say to the harvesters, “First collect the weeds and tie them in bundles for burning; but gather the wheat into my barn.”’”
As long as there are enough people with a good sense of the faith, the faith can be found like a pearl of great price. Seek it.