Because CPS can be pretty fucking terrible.
They are overworked, underpaid, and don't really care. They won't really help in most cases if you don't have a white, healthy child that, should nothing go right in your case, they can easily adopt out. I had my kid taken from me six months ago for smoking pot in my car before I picked them up and was pulled over. I'm facing a fucking felony over this and they wanted to stick our child in a foster home away from his mother and myself. I missed his first sitting up, his first standing, and fought fucking tooth and nail to get him back. If they hadn't fucked up so horribly by neglecting to even review our case, we wouldn't have gotten him back so quickly. My own childhood was filled with a violent drunk as a dad, but if I were taken away by fucking do-gooders like you, my whole world would've been fucking shattered. Taking a child away that isn't being sexually abused is just fucking wrong. It'll fuck that kid up more than staying with their parents.
I live in Texas, and you really need to look into how awesome CPS is here. OP should mind their own fucking business, maybe that kid is the only thing keeping them from killing themselves.
Fuck CPS and fuckers who think they know what's best for someone else's kid.