Someone on here emphasized that the reason it's better to take communion by mouth is so that the body of the Lord doesn't get dropped on the floor, stepped on, profaned by actions of the hands, etc.
The Extraordinary Form of the Mass clearly agrees with this, with many steps taken to prevent particles of the Host from getting in bad places (https://www.youtube.com/watch?v=2nToRDQeg_I), including cleaning all the items rigorously, and keeping the hands in a tightly closed position after consecration, pic related.
But here's what I don't understand (I'm not Catholic…yet anyway): after all, this, you take the Host in your bacteria filled mouth and then it gets torn up by vitriolic stomach acid, digested by various processes and the bilious liquids of the body…what makes this OK and different from the Host before you accept it?