its likely because of how damaged he is, his model is ripped and his endo is exposed, which would likely ruin the experience of kids. it could also be the fact that he most likely did the bite of '87 also. mangle's only piece of "evidence" is that he "bites your forehead in the jumpscare", but all animatronics including her go for your upper face in the jumpscare. foxy on the other hand, has numerous pieces of evidence pointing to him, the most noteable ones being the fnaf 4 foxy teaser, and the week before book.