Well, yes, it does make things easy for hackers. All they have to do is name the file containing their worm or virus $*****$ and the user will be unable even to see it.
Antivirus companies have been reluctant to deal with the problem, for fear of being accused of tampering with copy protection, which normally is a criminal offense.
AV companies typically check for viruses before they execute any programs, so once it is saved on disk it is basically too late. The only virus that uses the cloaking that I know of requires the user to click on an email attachment, then it executes and hides itself using the rootkit although it could have just as easily contained its own rootkit but that virus writer decided to be lazy.