and this is surprising because?
this may come as a surprise but they are rival search engines. you really think they WANT you to use their competition.
What your implying is that, say, wal-mart should have signs out front, "if you cannot find what you need here, try some other excellent stores, such as walgreens or Home Depot" And grocery stores should have their competitors flyers put out,
"CHECK OUT THE GREAT DEALS FROM OTHER STORES!"