Why doesn't smartphones have a voice interface?

I mean the command interface. What devices are the most natural to start having a voice interface? Mobiles of course!

We talk in them already. A voice interface to the PC isn't at all as natural. I can imaging people sitting at the office talking to the computer. Annoying, to say the least!

I have mainly used Sony-Ericsson and Nokia mobiles and in my old Sony-Ericsson P900 I could say the name of someone in the contact list. It work sometimes and if I said "Donald Duck" or something that P900 didn't understand I called someone randomly. Nokia never made any big effort to have the same voice input but my Nokia N95 and now Nokia E71 read up the callers name with a voice from an old robot-movie from the 70:s...

C'mon Nokia and Sony-Ericsson you can better than this! Can't you?

The Nokia E71 can even read up my e-mails and other stuff. Well not that bad but I have no use for it really.

So what am I talking about here?

I would like to have a voice input for every command you can do, such as "open calender", "book meeting", "start music player", "start radio" etc etc

It can be made more or less sophisticated but a basic level would be great. I wouldn't even need to put on my reading glasses! I have done many stupid things while driving my car, that I will not tell you about ;-) but a voice interface would spare me some tricky situations.

Can this be so hard? I know that the software for voice input is out there that can do these things so why not in the mobile?

Nokia, why didn't you go for this instead of 5800, the so called "iPhone killer". I tested it for one day. Really, I have to say this, it is pathetic Nokia! Your 5800 is like a modern version of my old Ericsson P900 when it comes to user interface. Yes you have many nifty funtions but an "iPhone killer"? You can't be serious! I haven't seen Sony-Ericsson's new "iPhone-killer" but something tells me that iPhone will remain the king of user interface for a while. So, Sony-Ericsson why didn't you go for something new? A real voice interface?

What do you say, wouldn't a real voice interface be a neat function to have in your mobile?

Maybe it is out already, did I miss something?