Took this off of mmo-champion:

We allow players to use macros for convenience, especially when automating tasks that they do often. Where macros cross the line is when they are making the decision instead of the player. In the old-days, there were addons that would essentially target a player with a debuff and cure it. That crossed the line for us – the mod was playing the game instead of the player.

In the /castrandom case, players were sometimes using these macros to cast the ability that wasn’t on cooldown without having to recognize this fact or hit the right button. Players using this system had an unfair advantage against players that weren’t. Instead of having to cope with the complexity built into the class, players could just spam one key and have the game “do the right thing.”

We recognize that in some cases, certain classes are probably over complex or else the default WoW UI doesn’t provide the information you need in a form where you can quickly notice that say an ability has proc’d or another is on cooldown. In these cases, we would like to fix the class or UI problem, not require all of our players to use macros to get around the limitation. You can help us identify those situations where you feel overly-dependent on a /castrandom macro so we can start to address those problems.

We also recognize that players sometimes used /castrandom for options that were truly random and with no gameplay consequence, such as picking a random polymorph animal, companion or mount. In these situations, we want to give you specific commands you can use to get the desired functionality. We have no problem with you rolling the dice in this manner.
Basically I'm not going to get comfortable with the 'click' method, because I'm sure they'll axe it soon.