I suppose that is human nature to some degree - "Oh he couldn't possibly be the killer." The example I give a lot of times with a sketch is the Morgan Harrington murder in Charlottesville VA. A year or so later DNA was tied to an attempted rape in Northern VA and there was a sketch of the attacker. When the sketch was circulated in Charlottesville, the employees at a taxi company made jokes about a co-worker, Jesse Matthew, about how he looked like the sketch. No one turned in a tip and Matthew would go on to murder UVA student, Hannah Graham, before he was arrested.It's actually happened quite a few times, and though it usually means a faster ID and arrest, in some cases the public remains flummoxed (see the Missy Bevers' case).
I think you're right about the video/still throwing people off. It could literally be almost anyone. Dude has to be one of the luckiest men alive right now because his looks and clothing are general and ageless. Also the disagreements over his facial features and what he may/may not be carrying or have on him. If I saw an image like that and my instinct was to say, "Hey, that looks like Jerry, the farmer next door", it would be hard for me to call it in because Jerry's a nice guy and I don't think he'd hurt a flea. So I'd already be on the fence about what I saw. But then I hear 10 people totally convinced that he has a beard and glasses I might think,"Well I don't really see those but everyone's pretty convinced...I guess I was wrong. Jerry doesn't wear glasses and has short hair. Good thing I didn't call it in!" Don't think people really do this? They do. They'll err on the side of caution and talk themselves out of calling, especially if the crime is particularly heinous, because they're afraid they may be wrong. People look for reasons to be talk themselves out of it being the person they know and it doesn't take much to sway them.
BTW, earlier this year LE announced that Jesse Matthew has stage 4 colon cancer. Karma's a real , Jesse.