It may not be required but its still a blessing. Give and you shall receive, the law of sowing and reaping is still in affect. Seed still brings a harvest, and if you sow sparingly you'll reap sparingly, but if you sow bountifully you'll reap bountifully. So whether you want to or not is up to you and your relationship with the Lord, and whether you wish to spread His kingdom and purposes. Its a matter of the heart, and don't do it grudgingly or of necessity (out of obligation), but from your heart and wanting people to be blessed and experience the Gospel.