You would be more accurate in your statement to say some Protestants believe that....but not all.
And I've answered your question already.
The Lord's Supper is a remembrance of His sacrifice on the Cross. We are not literally eating His flesh and blood. That would be a violation of the Law to eat blood....see the Jerusalem Council on this also.
The ECFs are not in agreement over this either.
If, as Rome claims, it was to be a literal eating of the flesh and blood we don't see it evidenced in the NT. There are no recorded events of the disciples or others attempting to capture His blood at the Cross or any other time.
Rome has greatly abused the Scriptures on this issue...as they do other issues.