I look at it this way: there are many, many good parents out there...and there are going to be some CPS/CAS calls that are unfounded (either intentionally or due to honest error on someone's part). Of those good and decent parents who are faced with a CPS/CAS visit, some will allow the worker to gain immediate access to their home and children and some won't... each set has their own reasons and own concerns. BUT, then there are the parents who ARE actually sexually or physically abusing their children, or are seriously neglectful, or have an incredibly dangerous home... I'm willing to bet that a whole bunch of them will refuse the worker access to the home and/or children. PLUS, there are the great parents out there who HAVE NO IDEA that their child could be being hurt or sexually abused by someone other than them- maybe in their own family- and so refuse the worker access/entry because they "know" that there is no abuse going on. A CPS/CAS worker doesn't have some sort of magic crystal ball that allows them to know whether they are being denied access to a child because the child is 1) honestly safe; 2) being hurt by a family who now knows that they are under the microscope and may flee/kill/retaliate against the child for "telling" or 3) presumed safe because the parent who refused access is not doing anything wrong...but is actually being hurt and has now missed their chance to get help. They need to ensure safety in case one of the last 2 things are happening.
I work in a school, and many CPS reports are made per year. Some, we have to report as mandated reporters although we sort of know that very little, if anything, will result. Others have been immediately horrifying... for example, we have had 2 different children removed from the home- FROM SCHOOL THE DAY WE CALLED becuase they reported sexual or severe physical abuse and CPS decided that they had to speak to the child before the end of the school day because it might not be safe to send them home. The most disturbing, acutallly, were the couple of calls I remember that we made somewhat reluctantly (not that we didn't know the call should be made, but that the child was insistent to us that there wasn't a big problem, we had "known" and liked the parents for years, etc.) and then when investigated, serious abuse/neglect was uncovered.