Hands are much dirtier than a tongue.
Reception of the Eucharist on the tongue is preferred by the GIRM. (General Instructions of the Roman Missal)
True enough! However, these are DETAILS. It doesn't MATTER.
We are simply BLESSED to have the Mass and Eucharist at all.
Remember what Jesus said that all that's "unclean" comes from within. I don't think He would cavil at dirty hands.