Pingbacks were a 0.1 implementation of a concept that never got a second chance, because then the walled gardens arrived and destroyed the ecosystem. The main problems they had were what you mention: each ping would contain only a few lines (which i think was a limit in the standard, to limit spamming) and the automation mechanism was a bit stupid (every reblogging ended up generating a superfluous ping). People who cared could fix the first issue (with a sort of "above the fold" summary), but the second was enabled by over-eager engines and ended up ruining it for everyone.