Receiving the Eucharist is one aspect of attending Mass. Another aspect is giving worship to God.  I agree that we probably do well not to receive the host while dancing and singing, for reverential and logistical reasons, but I can't see why movement, and song, should not be part of  worship. Why would one not worship God with one's whole being?  As our priest sometimes notes, a stone can praise God, but worship is something different, something more.