I decided to research why there are different materials or traditional anniversary gifts for each year of marriage. The following is some interesting explanations of why these traditions are the way they are:

Every anniversary celebrates a moment in the journey of marriage. The passing of another year togerther marks a deepening of the couple’s commitment, and accumulation of time irreplaceable. To help in celebration these occasions are special gifts, one assigned to each anniversary and each with itys own material and symbolic value. In the United State, the wedding anniversary symbols begin simply, with paper and flowers, and gradually increase in substance and value. The order of the gifts reflects the investment that couples gives of themselves to each other – Source The Meaning of Wedding Anniversariesby Ann Field

This explains the interesting concept of why the first anniversary gift consists of paper (although paper sounds quite boring, there are a lot of great paper gifts you can give your spouse, from a plane ticket to a framed photograph) and why a twentieth anniversary gift consists of something a bit more fancy like china.

According to Tokenz.com the history of milestone anniversaries is:

In the medieval times only milestone anniversaries like 25th and 50th were celebrated. To mark the occasion of Silver or 25th wedding anniversary a husband would crown his wife with a wreath of silver. Likewise, he presented her a wreath of gold on a Golden or 50th wedding anniversary.

By middle-to-late 1930s, people began to celebrate 1st, 10th, 20th and 70th anniversary along with 25th and 50th. A gift for each of these milestone anniversary years was also decided by the society. The logic of presenting gifts was that stability deserves a reward and more the stability the greater should be the reward.