Because there are numerous examples of companies misidentifying photos of young children in non-sexual contexts as CP, creating legal and other problems for their parents. This is especially problematic given that even if you're legally cleared, even just being investigated for this reason is a massive social stigma (because the moral panic around CP is so extreme, it thwarts presumption of innocence, due process etc).

https://parenting.blogs.nytimes.com/2009/09/21/are-bathtime-...