It is actually an error to do so. But no one seems to know why. Yet the reason seems perfectly clear to me. It is because of the Eucharist.
The Eastern rite Liturgy is called the Eucharist, the Love Feast and Our Lord’s Table. It confects a true Eucharist in all regards. But it is never called the Mass because it does not celebrate the Eucharist with Masah. Masah is the Greek word for unleavened bread. It goes back to the Hebrew, “matzha”. Which dates all the way back to the time of the Passover which was celebrated with unleavened bread.
The Western rite (i.e. Roman) Liturgy has always been called the “Misa” or Mass because it celebrates the Eucharist with unleavened bread. As the Scripture says:
Exodus 12:15 Seven days shall ye eat unleavened bread; even the first day ye shall put away leaven out of your houses: for whosoever eateth leavened bread from the first day until the seventh day, that soul shall be cut off from Israel.
1 Corinthians 5:7 Purge out therefore the old leaven, that ye may be a new lump, as ye are unleavened. For even Christ our passover is sacrificed for us:
If the Mass were a derivation of the word “dismissal”, you would expect the same to be true in the Eastern rite, since they also have a dismissal. Yet, that is not the case.