The Golden Age artists were also commercial artists, which makes all the difference. Frank Quitely, Jim Lee, Ivan Reis, and the rest of the modern comic artists targetted the comic book industry. With few exceptions, in the '40s, artists would have been almost itinerant, hoping for an eventual "real job" at an advertising or drafting company, so their work reflects that more realistic craft.
Personally, I think it makes everything look better, and it's a shame most of what we have today are artists from the scritch-scratchy make-everybody-look-constipated-and-don't-worry-about-anatomy school.