When you put in a "within X miles" on our site, we only pick a few of the largest airports within that radius, not all airports.
Even if we didn't do that, we only consider a few hundred of the fastest flight options between the origins and destinations, regardless of how many origins and destinations there are. While this might find some interesting routes and prices, it's certainly not a very comprehensive search.
Doing an "everywhere to everywhere" (or even "everywhere to somewhere") search is not something you can do very effectively with our site.