Yeah, I was expecting something closer to "because that's what people Google for".

A big part of designing a security-related API is making it really easy and obvious to do the secure thing, and hide the insecure stuff behind a giant "here be dragons" sign. You want people to accidentally do the right thing, so you call your secure and insecure functions "setHTML" and "setUnsafeHTML" instead of "setSanitizedHTML" and "setHTML".