Not to nitpick, but there are TWO types of "good singers". One is the Natalie Maines, belt it out (although she's too nasal) lead singer, and the other is the kind of singer that has such control over their pitch they can sing in perfect harmony every time. I do believe the sisters fall under that category.
I'm a little biased, because I am primarily a harmony singer.
Hey, you'll get no argument from me. I've been backing up the Tenors for years.
Emily and Martie sound great when they are providing the groundwork for Natalie's lead, and that is an important function. There are not many people who can do that well. A lot of people who can sing lead vocal can't do it. Linda Ronstadt and James Taylor can, but not many others. Maybe it's an ego thing.
It is very savvy of the Dixie Chicks to have everybody doing what they do best, with this one exception. As I say, I am a big fan of their music. It's a shame about their politics.