For most of the Silver Age, DC did not include credits for their stories (although it was not uncommon for artists to sign their work). Indeed, probably the most common credit given was fictitious; the one that identified most Batman stories as being drawn by Bob Kane.
Marvel was different. From the very beginning, they included some credits for their stories. From Fantastic Four #1:
Although these amusing credits became a significant part of the difference between Marvel and DC, they did not last anywhere near as long as I remembered. Indeed, by late 1966, Stan pretty much reverted to a more basic style:
The appeal of these credits was strong. It gave readers the feeling that they were in for a fun time. True, the self-promotion could get overbearing at times, but this was also the era where Mohamed Ali amused us all by proclaiming his greatness at the top of his lungs, rather than engage in the more common false modesty of most athletes before and after.