I think Yahoo knows it can't compete with Google in search results, so why creating a page where the only thing you can do is experience crappy search results and nothing else?

At least this way they're attracting a niche of people who do like a more portal like search engine. And in some places that niche is the majority of the population, like in Japan, where Yahoo seems to be very successful.

If the users just want a search box they have http://search.yahoo.com/. I don't know if they can customize that do be the default.

So the thing "Yahoo don't quite get it" doesn't seem right to me.