Why is Siri no longer pulling from WolframAlpha?

In the past I remember being able to ask Siri, for example, what the volume of a sphere radius 3 was, and it would tell me using Wolfram. Now when I try, it simply says "Here's what I found on the internet" as it does a Google search for the question. Does Siri no longer pull information from Wolfram, or am I messing something up or missing a setting?