I can understand why they've done this, it's because there are so many 'no-brain DPS mash' and 'I-win'macros out there that use /castrandom. It's the 'no-brain'/'I-Win' bit that annoys them, they want skilled players to have an advantage over those who just want to press one button again and again.

It sucks if you're a multiboxer though, even more so if you want a mixed team.