Becaues first of all, Jesus chose bread and wine when he instituted the Sacrament. He didn’t choose a piece of meat, even though he had meat available at the meal.
Second, the physical form of the Host doesn’t change when the transubstantiation occurs. It is Jesus’ body. “Truly hidden behind these appearances” of bread and wine.*
It’s rather a good test of faith, I think, because to the outward senses, nothing looks to have happened.
Which St. Thomas Aquinas noted in his Adoro te devote prayer.
*I edited out the part of my post that Titivillus quoted below because as they pointed out, there is a legitiate concern that the way I wrote it sounds like the Lutheran doctrine of “Consubstantiation” which is that the bread continues to co-exist alongside Jesus’ body. This is a theological doctrine beyond what we’re talking about which is 'why doesn’t it look/ taste/ feel like meat" but in order to avoid confusion I changed it. Titivillus has expressed the correct theological view below.