While it is often trivial for interested/curious people to figure out with reasonable accuracy who the person with name suppression is, we should also consider its reduction in impact.
While suppression might be pointless at keeping everyone from knowing the identity of the individuals involved, it is still very effective at keeping the identity out of the news media. In this regard, it is very effective at avoiding wall-to-wall, blanket 24x7 coverage of the individuals, which media organizations tend to run during high profile cases. Such coverage could have serious effects for victims or the accused, if found innocent or otherwise*. I would argue that we should measure it's pointlessness on these parameters, rather than it's absolute watertightness.
*After all, media organizations tend to use 'allegedly' left right and center, in order to say whatever they want.

