If I get some knowledge through a Google search, I can publish it without attribution and use it commercially without pay. Not so with Alpha. Yes, I cannot offer users a service based on mass-remixing Google search results, but this is another matter and much more reasonable.
Nor can you with Google: someone wrote the page you found using Google, which in all likely-hood has it's own terms of service and associated copyrights. Copyrights you would infringe upon by republishing without payment or attribution.
Ah, but facts aren't protected by copyright. Wolfram Alpha deals a lot in hard facts, so presumably we're also talking about finding facts with Google.
