The well-publicised deaths themselves are of course the biggest warning to deter others. But this can also make reaching the summit even more of an attraction, and achievement, for the dare devil - or even someone just seeking a bit of "adventure".
One thing that could be done is to clearly re-classify fedders as a rock climb (in the "free solo" style), not a bushwalk. Whilst what people post on individual blogs cant be easily controlled, Parks can take some responsibility for this. The Parks page for the Eastern Arthurs currently states that walkers need to be confident with "cliffs and rock scrambling". That's an understatement for summitting federation peak. It goes on to say "the Eastern Arthur Range Traverse challenges experienced walkers and rewards them with the celebrated Federation Peak (1225m). A mecca for walkers and climbers everywhere, Federation Peak is an imposing quartzite mountain with sheer faces and formidable jagged edges." This makes it sound quite enticing, no doubt written by the marketing team.
Although people who choose to attempt this walk ought to undertake their own research, and therefore be aware of the risks, it is still likely they are more experienced at bushwalking than rock climbing, and perhaps underestimate the rock climbing skills and mindset required (more than "confidence"). There is obviously a cross over between the two when scrambling is involved in reaching a peak, but fedders seems to really take it to another level with little room for error.
I'm aware that my own bushwalking experience and capabilities would only be sufficient to get me to the base (if that). I would need to dedicate a couple of years to learning rock climbing skills and dealing with heights, and even then make a careful assessment of my own limits before attempting. But of course even doing all of that, the risk remains.
In the end, why do people do it? Well because it is there.