I wrote about this problem here ( http://serv.github.io/blog/2014/02/20/unfortunate-state-of-m... ). Mobile Web sucks because there's an incentive problem. No one really has strong incentive to make mobile web better. Performance issues are largely an effect of this root incentive problem. (edited from "cause" to "effect") - Users have a strong preconceived notion that websites on mobile just suck compared to native…
And, as mobile screen sizes and 4G availability increase, it seems that it would be less of a problem running full-site versions on mobiles going forward.
Maybe more of this issue will resolve as Apple moves to larger screen sizes, but I have always had the impression that mobile-sites were a stop-gap until higher-bandwidth and larger screens became the norm. Reminds me of the short-lived WAP standard before smartphones became de rigueur.