Why is the growth of the value of dividends significantly lower than
the growth of the value of stocks in the S&P 500?
The 500 companies that makeup the index determine if they pay their shareholders dividends, and how much. The index and the fund play no roll in this decision.
In general companies have determined that paying dividends isn't something that their shareholders want and expect. Some companies still pay dividends, and they consider this to be an integral part of their culture. Others have said we can use the money that would have gone to dividends to grow the company.
This lack of dividends was especially true with the rise of tech companies that were founded since the 1970's. They grew the business based on their profits. Sending a portion of their profits to shareholders wasn't part of the plan.