I've noticed lately that many times things I know Alpha will slam-dunk don't get routed to it by Siri. I'm not aware of the details of the deal we have with them but from my observations of Siri it looks like Apple might be looking for certain keywords (such as how, what, why, etc) before it tries routing anything to Alpha. I hope they can relax that in future.

Luckily if you say "Wolfram XXX" instead of just "XXX" Siri will route your question straight to Alpha no-questions-asked.