Not having a pic may have been ok in the days of dialup, but most people view this as a dating site. So a pic is necessary anymore.
People want to know who they're talking to. You don't have to be model perfect. Just real. Having your picture easily accessible makes you seem more "real" as opposed to a faceless profile.
Me, I generally don't even bother sending messages if there's no pic in the profile. If they message me first, I'll ask for a pic if/when I feel it's appropriate in the conversation, or necessary for me to care, or if I don't know what else to say but want to continue the conversation.
But I'm shallow as fuck. And single as fuck. So what do I know?