I think it true, yes, most scammer not bother to make video. But also not most ordinary honest people too. 
Anominity highly important to many in Bitcoin, and a video of the self break that and hurt the privacy. It also bit embarrass to make video of self ask for $10 or $20 of the bitcoins. Many people also feeling shame for posting any video or picture of the self to forum because some people might make fun for having fat or being unattracting. It just not something most people in bitcoin want or willing to do...
Anominity highly important to many in Bitcoin, and a video of the self break that and hurt the privacy. It also bit embarrass to make video of self ask for $10 or $20 of the bitcoins. Many people also feeling shame for posting any video or picture of the self to forum because some people might make fun for having fat or being unattracting. It just not something most people in bitcoin want or willing to do...