I'm not saying that it necessarily shouldn't apply everywhere else, but it's certainly a fact that in those industries the business is _not_ the idea (at least at that grand scale). The business is the timing and follow-through. Abstract ideas are a dime a dozen in most industries. The idea of providing an improved search engine, or simplifying financial transactions is relatively trivial (for each of those companies there were certainly hundreds of failed ones that all had the same grand idea). (This triviality is in contrast to the specific method--for example, PageRank--that was used in the case of Google.)

As a side note, why do you believe that it doesn't apply outside those industries? I'm sure if you asked Brin and Page, they would say they were inspired by (the limitations of) previous search engines. Ditto for Stripe and Paypal and Facebook and Myspace.

Academic ideas are (hopefully) much more specialized than these broad ideas. In business they are more comparable to patents and for patents prior art is of course extremely important (enough so to legally invalidate your legal claim to your idea!). In contrast to patents, however, there aren't strong legal mechanisms to enforce priority of ideas and that's why being honest and open about it (community policing of these ideals) are especially important. If academics were to entirely stop caring about citing their sources, academic research would probably totally cease to function.