Publishers are interested in the ESRB rating because a lot of retail stores (e.g. WalMart) will not stock unrated games.

If you have a good publisher, you probably will not have to worry about getting rated (other than the fact they will probably subtract a "rating fee" from you royalty check) but, when I think about indie developers, I also include self-published developers (I'm sure a couple of you fall into this category).

Not every developer is working on a game that will attract a publisher, so it is important to keep self-published games a possibility.