Where the creativity HASN'T gone on cable

As this season of The Walking Dead draws to a close, it reminds us how how great cable TV--once the province of wrestling and Andy Griffith reruns--has become.  With tight scripting, intense characters and even serviceable CGI, cable has become a go-to outlet for great TV.  Even apart from HBO, cable has given us Mad Men, Breaking Bad and The Americans.

More than one critic has complained that, if anything, cable gives us too much good programming to watch.

So why do ads on cable TV fail to engage as well as the programming they fund?  More to the point, why hasn't this haven for direct response TV advertising (DRTV) emerged as laboratory for breakthrough creative?