Rights issue - signaling of directors?

I read the following somewhere: "The success of rights issue will depend on the willingness and ability of the director-shareholders to subscribe." Why is this? Is this because of asymmetry of information (directors know more than outside shareholders) and signaling or some other reasons? (The context was that director-shareholders might not have the funds to take part of the rights issue and that would cast doubt on other shareholders taking up the right issue.)