What are some of the most difficult things to do on a large screen smartphone? Type long complicated messages. Even harder, if you have to switch between fields like in a calendar to make an appointment. How about sorting through pages of inaccurate Google search hits?
If you use Siri, you will find the following become immensely easier:
Manipulating you calendar
Accurate search of databases (thanks Wolfram)
Finding local places of interest.
All of this done without extensive training on the user's part. Siri has made use of these features oh so useful and easy now. But, people are not used to it. But you know what happened at Apple? They tested the idea for month and months, in order to solve a severe cuatomer hassle, then when trying the old way of doing things, the end user benefit was clear. Rubin, Lee, Balmer, pick your favorite, are not designing user experiences. They are copying and adding some small feature differences.
Critical to all this is both recognition accuracy and understanding context. If you have not gone down this path, then you are going to be of the opinion it is a minor feature. Why, because rembering syntax (like programming) takes a lot of effort.