Managing Data Usage in ICS: A First?

Adding a way to effectively set a limit for data usage on your phone (I think) is one of the best elements added in ICS. Gone is the worrying about where your current usage sits and with that, the possibility of surpassing your allowance and thus charged extra. This is excellent from a consumer standpoint!

It looks extremely simple to set up and has a nice graphical interface. Just slide the bar to your own data cap and you're done! The ability to set your own custom threshold for a warning is great as well. (Maybe even include the ability to add another or more sliders for additional warnings to set at certain custom intervals in the future?)
This wonderful feature almost makes me want to not have unlimited data, just so I can utilize it. (Almost, but not quite.)

So this brings me to my question: Why wasn't this feature implemented in all other smartphone OS's in the first place?

I'm not talking about using an app that you can go and download, but actual integration.

  • Is it because carriers wouldn't want it for the reason that they profit when customers accidentally exceed their limits and have to dish out more money?
  • Or is it genuinely that no one has thought to do such a thing before?

(Or, has it been done previously and I just don't know about it?)