As much as I would like to see browsers having nicer default styles (and all browsers ignoring website CSS), it will never happen because too many websites will break as a result since many of them implicitly rely on certain defaults like black text on a white background, link colours and other stuff.
I feel like browsers could improve their defaults without breaking that: make the background slightly off-white, text slightly off-black, add some small margins at the edges. Or even just import the Bootstrap 2 stylesheet as a default.
Been there. In Konqueror (oh the olden days), the default colors came from the system color scheme. When I was using an inverted color scheme (White on Black), some websites were unreadable because they set the text color to something dark, but left the background color at the default (which was implied to be something light, but was actually dark blue for me).
