Is this because it no longer makes sense to track the DJIA? If so, why?

Some reasons come to mind:

• The DJIA consists of only 30 companies, so it is more risky since one company can make large changes in the index. Other indices have hundreds of companies, making them more diversified and less risky.
• Th DJIA is not market-cap-weighted like the S&P 500. Market-cap weighting is good for index trackers because they rebalance automatically (if a company's price increases, it's market cap also increases, no no rebalancing is necessary). The DJIA is evenly weighted, so if a company's stock increases, its value in the index will become disproportionate, and the index must sell some off to balance out the value. This creates a lot of churn and increases transaction costs.
• The S&P 500 contains all of the Dow 30 stocks, so there is a high degree of correlation between the two.
• The constituents of the Dow 30 are determined by a committee of three people, not by defined criteria, so there's more possibility for human bias in the constituents (this may not make a significant difference, but it is something to consider)

The DJIA is easy to calculate (it's an arithmetic average of stock prices divided by a factor) so it is a decent measure of the market, but it's more complicated to replicate and arguably a less accurate market indicator than other indices.

Is this because it no longer makes sense to track the DJIA? If so, why?

Some reasons come to mind:

• The DJIA consists of only 30 companies, so it is more risky since one company can make large changes in the index. Other indices have hundreds of companies, making them more diversified and less risky.
• Th DJIA is not market-cap-weighted like the S&P 500. Market-cap weighting is good for index trackers because they rebalance automatically (if a company's price increases, it's market cap also increases, so no rebalancing is necessary). The DJIA is evenly weighted, so if a company's stock increases, its value in the index will become disproportionate, and the index must sell some off to balance out the value. This creates a lot of churn and increases transaction costs.
• The S&P 500 contains all of the Dow 30 stocks, so there is a high degree of correlation between the two.
• The constituents of the Dow 30 are determined by a committee of three people, not by defined criteria, so there's more possibility for human bias in the constituents (this may not make a significant difference, but it is something to consider)

The DJIA is easy to calculate (it's an arithmetic average of stock prices divided by a factor) so it is a decent measure of the market, but it's more complicated to replicate and arguably a less accurate market indicator than other indices.