I think people have recognized his voice and have either second-guessed themselves and talked themselves out of turning in the tip or the tip got lost in the shuffle or (for whatever reason) the evidence they have isn't pointing to him. Even when they put out a sketch of Ted Bundy and released his first name and vehicle, his friends just joked around that it might be him. The more "normal" this guy appears to be, the less likely those in his life would probably be to think he's BG.
The man on the farm next to mine is a widower. He's in his 70s and has been good to my family. He volunteers for everything in town. Is a retired railroad employee. Sits on the water commission. Rescues animals. Comes over and helps us out and, occasionally, drops by with pizza and sandwiches from his son's restaurant. If 2 teen girls were violently murdered and a sketch was released that sort of resembled him, and a 2 second video that sort of looked like the way he moves came out then those of us who know him would probably just laugh. "Ha ha ha, that looks like Jerry. Jerry, did you kill anyone? Ha ha." We'd all be shocked as hell if we found out it WAS him. Some people wouldn't make the call because they'd be afraid of being wrong. And some people wouldn't call in because while they might see a resemblance, they wouldn't in a million years think it was actually HIM. And then some people wouldn't even see the similarities at all.
I think we often confuse lack of arrest with lack of identification. It is entirely possible that someone has recognized him but hasn't done anything about it.