Why isn't Jesus called Emmanuel?
For Matthew the importance of the name is not that his name is literally Emmanuel but that he is "God with us."
Matthew fleshes this out later in the Gospel in two passages:
- For where two or three are gathered together in my name, there am I in the midst of them (18:20)
- And behold, I am with you always, until the end of the age (28:20).
Matthew was clearly aware that Mary and Joseph did not name their child Emmanuel. However, he sees the meaning of the name Emmanuel ("God with us") as being perfectly fulfilled (Is. 7:14) in the fact that Jesus is the presence of God.