"But then I can't see as many windows!" That brings us back to the GP's I need to see what I'm looking at, not what I'm not looking at". When you want to look at those other windows, bring them to the foreground and let them obscure this one.
Seems like the same amount of characters that are each wider would be wider? So you would see less characters on a line with the same amount of characters
Well yes and no. The line would visually become longer, but if we're talking enforced line length by IDE's, say 80 characters, then the line would still be 80 characters long, but just take up visually more horizontal space and so whether or not you see the same amount of characters on a line would become an issue of how much horizontal screen space do you afford for code.
I think it increases readability. I need to read what I'm looking at, not a lot of things I'm not looking at.