In my opinion, the very best purpose of the Christmas Tree is the following:

The Beautiful Tree of Christmas ~ by Bishop Jerry L. Ogles, Anglican Orthodox Church
Jeremiah 23
5 Behold, the days come, saith the LORD, that I will raise unto David a righteous Branch, and a King shall reign and prosper, and shall execute judgment and justice in the earth.
6 In his days Judah shall be saved, and Israel shall dwell safely: and this is his name whereby he shall be called, THE LORD OUR RIGHTEOUSNESS.
What a blessed and wonderful time of year for all the world, but especially for Christian men, women, and children! Several years ago, I was passing through Tokyo and Hong Kong during the Christmas season and observed extensive Christmas decorations abounding throughout the two cities. Most of the decor was tinsel, lights, and, of course, Santa Claus. I was impressed by the fact that Christmas is celebrated around the world, but mostly by people who have no idea of its meaning - even professing Christians who place Santa, or gifts, or decor, at the center of their observance.
Symbolism is an important aspect of Christian worship. The cross, the candlestick, the bread and the wine are all symbols of a higher spiritual entity. We do not worship the Cross, or the candles, etc, but what they represent. Christ taught in symbols of thing earthly which pointed to things heavenly. One such symbol is the Christmas Tree which is an evergreen tree decorated with lights and beautiful trinkets. These remind us of the beauty, light, and eternity of our Lord.
One of our primary Christmas customs is to place a beautiful Christmas Tree in our homes. It is decorated with all manner of bright lights, colors, ribbons, and Christmas ornaments. Like our Lord Jesus Christ, the Christmas Tree is full of lights. It brightens our holiday and makes us glad. But have we left something out? Something vital and crucial to Christmas? What about the Sovereign Lord in whose honor the day is named: the Lord Jesus Christ?
The Christmas Tree may remain a center of attraction, but perhaps we should look beneath the tinsel and icicles to see the symbolism it can have in our homes. Long ago in the Garden at Eden, the Lord God fashioned a Paradise for the crown of His Creation - Man. In the Garden, He placed many beautiful flowers, trees, and herb-yielding plants; but at the center of the Garden He placed the Wonderful Tree of Life. Along with the Tree of Life, the Lord God made to grow the tree of the knowledge of good and evil alongside thereof. GENESIS 8 And the LORD God planted a garden eastward in Eden; and there he put the man whom he had formed.9 And out of the ground made the LORD God to grow every tree that is pleasant to the sight, and good for food; the tree of life also in the midst of the garden, and the tree of knowledge of good and evil.10 And a river went out of Eden to water the garden; and from thence it was parted, and became into four heads.

Man has always sought to go his own path apart from the leading of God. He has attempted to do all things according to the will of his flesh, and not the counsel of the Holy Spirit, to the detriment of his soul. Man did not find the TREE of LIFE so appealing as the tree of the knowledge of good and evil. Man was proud and did not want God to withhold any secrets from his knowing. Pride led to the downfall of our ancient parents when Eve succumbed to the temptation and lie of Satan that if she ate of the forbidden fruit of the tree of the knowledge of good and evil she would “become as God” The Tree of Life was avoided in much the same way that it is today. Our Christmas Trees can uplift our love for Christ and be a testimony to the World. He is the Tree in the midst of the Garden. He is the evergreen branch of righteousness which is changeless with the passing of the seasons. His branches are ever full of Life. He is the Light of the World and the Torch of Truth which may be represented by the Christmas Star atop our Tree of Christmas. His earthly life began as he was laid in the heart of an earthly tree - the manger, and ended some thirty years later on a tree of shame and infamy; yet, His great sacrifice brought eternal life and Redemption to all who believe and will partake of the Tree of Life.
This Christmas please remember to keep the true Tree of Christmas as a joy and symbol in your home. God rest ye merry gentlemen, joyful ladies, and bright, young children in the Light of His Christmas Light and unfailing Love.