1 Nephi 4:15

15  Yea, and I also thought that they could not keep the commandments of the Lord according to the ^alaw of Moses, save they should have the law.

            -People are simply not able to keep the commandments, which brings happiness and joy, if they do not know what the commandments are.  Hence, people cannot be truly happy and at peace until they have the gospel.  We cannot be saved in ignorance (without a knowledge of and obedience to the law) neither can we have happiness in ignorance.  We are providing a GREAT blessing by making known to people the truths of the gospel; its laws and ordinances.  Giving the gift of eternal truth is the greatest gift we can give another person in this life.  This is not a single gift, it is composed of many parts (like various Lego kits).  We can, for example, give the gift of godly love to another person.  This is but one part of eternal truth but will bring tremendous happiness. We can then give the gift of a knowledge of modern prophets.  This is another part of eternal truth.  Giving scripture (i.e. the Book of Mormon), ordinances, doctrinal truths, laws and standards, etc. to our children, family and friends will each increase the happiness of those who embrace these gifts.  Many around us, however, do not even know what heavenly gifts are available to them and are living on only a portion of the larger happiness that is available.