Why Support Missionaries?

There are many scriptures that talk about missions and missionaries. God's word calls all believers to spread the gospel to all the world. Consider the following scriptures:

Then saith he unto his disciples, The harvest truly is plenteous, but the labourers are few; Pray ye therefore the Lord of the harvest, that he will send forth labourers into his harvest. -Matthew 9:37-38

And he said unto them, Go ye into all the world, and preach the gospel to every creature. -Mark 15:16

As they ministered to the Lord, and fasted, the Holy Ghost said, Separate me Barnabas and Saul for the work whereunto I have called them. And when they had fasted and prayed, and laid their hands on them, they sent them away. -Acts 13:2-3