Because that is exactly what it will be if the Anonymous function affects it.
The Friends' List lets you keep tabs on people you enjoy playing with, alts of friends, and sometimes of people to avoid. And with all the new additions, it will make knowing what your friends are up to even easier and much less hassle.
But not if anonymous affects it. If becoming anonymous, also makes you anonymous, there was no point to even put in this system. All the features are useless if you can't know if one of your friends is online, which is the whole point of a friends list.
For one reason or another, many people prefer to remain anonymous the majority of the time. For some, it is to avoid plat farmers/sellers. Being anonymous significantly reduces the amount of tells and spam mail one receives. Other people remain anonymous because they don't want to be harassed with tells to group for such and such quest 20 times while they log in. And others want to be anonymous because they just want to log on for 15 minutes and check an auction without getting spam invited.
One of those problems deals with those plat farmers. I understand there's not much Turbine can do against them, but they exist, and most people would rather go anonymous rather than have to ignore the tells and spam they get from them.
The others have to do with people desperate for group members they go outside of the LFGs and look at just the people online. That may be because the LFG/LFM system needs more work. Or perhaps people need some education in what LFG means.
The point is, for whatever reason, a vast amount of people are anonymous. If the Friends' List regards those people as off-line, there was no point for all the development time that was devoted to it.
I ask that the Developers please reconsider their decision. Or come up with some alternative method of adding friends, or triggering anonymous. Some people suggested two different anonymous statuses. One for the general public, and one for the Friends' List. I don't see how the implementation of it would be that difficult.
If anyone agrees with me that this is a bad decision, please post below. Let's not let such a great feature be rendered useless because anonymous affects it.