It is a historic thing. Once (ie the 1950s) calculating the S&P500 took hours - newspapers did it after the market closed for the night and the number was one of the last things put into the paper before printing. The dow could be calculated in a few minutes so radio and TV could report on it. Thus if you were a trader focused mostly on one stock, updates on the dow gave you a picture of the market - if the dow was moving it was a clue that there might be larger economic forces in play that you need to look into so see how it affects your stock.

Today we can calculate all the indexes several times a second. Thus the value of the dow (something easy to calculate) is not important today and we shouldn't use it.

No one is forcing you, but when the cultural zeitgeist is behind it (reported every day in the pop news, especially when rising) it promotes mass financial illiteracy.

I think it's a lost cause, just like the metric system in the USA, but dropping the Dow and focusing on more accurate measures would, in a small way, focus people's attention on more important economic news.