They're spineless because they're at the mercy of tournament officials and sponsors who rely on those very players who violate the rules to host a successful event. A sad state, to be sure.
Maybe in the case of Nadal/Del Po taking too much time or Roddick/Safin bitching at officials, etc. But still even with some of the less marquee matches they are pathetic. How many times can David Ferrer, who probably has absolutely zero star appeal outside of Spain, get away with very obvious on court coaching? And why?
Then again we do want the rules to be fair and equal. Nadal, Del Potro, Djokovic etc. should not be above the rules.