Is it only me that finds New York magazine cover to be a bit distasteful? Someone is accused of a horrible crime, and the victims all choose to line up to be on the front cover of a magazine, like they're celebrities. A media circus over the issue is hardly good for a fair trial.
You're right, unfortunately when a celebrity is involved it is very difficult to even get to a trial, especially in cases of rape.
Many people, when raped, do not tell the police immediately. There are many reasons for this:
1) They might not want to tell people it happened.
Rape is an intense personal violation, and to admit that it happened to you changes how people see you. They might not want to admit it even to themselves.
2) They might think people would blame them.
This is very common with rape. That someone was wearing revealing clothes, or chose to walk home rather than take a taxi, or was drinking, are common ways that a victim is blamed for rape. To clarify here, the only person to blame for rape is the rapist. It doesn't matter what the victim might have been wearing, where they walked, how they behaved.
3) They might think people wouldn't believe they were raped.
People vastly overestimate the percentage of rape cases where the accuser admits it was a hoax. In common with most crimes, it is (IIRC) around 5%. It doesn't help that rape is not something that necessarily obvious evidence like broken windows or black eyes. The evidence left behind is in an intensely private place, and, especially after such a violation, you probably don't want people peering down there.
4) They might think their rapist is untouchable.
This is especially prevalent in celebrity cases, as Operation Yewtree has shown. There were allegations against Jimmy Saville and other celebrities for years but nothing was done about it. Celebrities hold positions of power, and can easily make life miserable for others to hide their own indiscretions. Cosby acted as a mentor to many of the people who say he raped them, and even in an abusive relationship it can sometimes seem a better idea to just let it slide.
5) They might not even know they were raped.
This may not seem so easy to believe, but if you were unconscious the entire time, you might not know you were raped. You might not even know you'd been drugged.
6) Even if they do stand up and say they were raped, their rapist is unlikely to ever be prosecuted, and even more unlikely to be convicted.
Rape, as mentioned before, does not generally leave lasting physical evidence, and so it often boils down to a "he said, she said" issue. Prosecutors are unlikely to go for these cases as the chances of winning are fairly low.
In all such matters, there is strength in numbers. For the earliest victims, the statute of limitations has long passed, so all they can do is stand up now and help others who were similarly abused get the justice they were denied.
As an aside, do you know why the Cosby allegations came to light in the past year or so? They'd been swirling around him for ages, but what brought them to media attention was a comedy act. I kid you not. Hannibal Buress started putting "Bill Cosby is a rapist" in his act, and that was what got media attention. Cosby had even admitted under oath that he drugged women before having sex with them, but the media wasn't interested.
For more information, see the Vox Card Stack regarding the Cosby rape allegations:
http://www.vox.com/cards/bill-cosby-rape-sexual-assault-allegations
