You can assume that some, and maybe most of the people watching certain videos are kids, but there's no way to know for sure since the account itself is for an

You can assume that some, and maybe most of the people watching certain videos are kids, but there's no way to know for sure since the account itself is for an adult. Just like on a porn site, you need to agree that you are an adult, but realistically a lot of non-adults probably are watching too. The question is, if in the user agreement you agreed that you are above 13, but then you aren't, is that the websites fault? Now it's up to Google to 1. figure out which videos (uploaded by others) are for kids, and 2. automatically assume everyone watching said videos are kids. Both of those steps are rough approximations. The better solution is to stick to the EULA and have kids actually use Youtube Kids, instead of "guessing" what videos and users are.