It justifies why they do it (money), it doesn't justify it being the right thing to do. If they want the money over their child's future feelings then sure, that's their choice. The kids could have the experiences without their parts being filmed. I did say Stephen and Jess can do what they want with their own images. If their content was good enough before kids to obtain viewers, they should be comfortable in only filming themselves for public vlogs. Even if there is no law, there is no way in this day and age that they would not have seen the increasing and on-going narrative from ex-child stars/family vlog children etc talking about how their negative thoughts, feelings and experiences. That should be enough to change their thoughts about what they're doing with their own children, arguably you shouldn't need laws to tell you to partake in decent common courtesies like not exposing your child to millions of people before they can properly consent.
That's regardless of - again - the literal police asking people to stop posting so much about their children for the safety concerns.