What is it about men who can provide that women find so attractive?

Anecdotal only, but I think (in general) women have an inherent "nesting" gene.  Based on the urge to nurture and care for the family and home, they "generally" want to have someone provide for them so they have an environment in order to focus on their nurturing nature.

I'm not rich, but bust my tail working.  We're about to have our third child, and my wife didn't go back to work after our second.  BUT she's making money doing what she loves on her time from home while being able to be a full-time mom, which is her dream.

Exception: Gold-diggers or lazy women who want someone to support their nasty spending and apathetic habits.

And of course, as I've stressed, this is a generalization based on my social and personal experiences.

Women find "men who can provide" attractive because it increases the chance of survival of the children they have. Woah! Wait a second, you say. How the f*** does that work? It's a rather simple concept to understand: because of the long gestation period (ie a 9 month pregnancy) and also the long development period of children (ie 18+/- a few years) having a child is extremely costly for a woman. Therefore, it is advantageous if the woman can find herself a mate that will help her through her pregnancy and then stick around to help her raise the child. Choosing such a man thus increases the chance that the child will survive.