Why do airports have directional runways instead of a large area to operate in any direction? Instead of a few runways in a few directions, why not have a large square block of asphalt so that planes can take off and land in any direction? Where and on what direction planes land and take off will still be determined by ATC, but these decisions are then not bound by the choice of just a few runways. So, there will only be virtual runways and taxiways instead of real physical ones.
The typical World War II "A" runway shape solves this issue, without covering a huge amount of area with concrete, etc. Even so, that configuration has fallen out of use in modern airports. 

Ultimately, this is a solution to a problem that doesn't really exist and a problem which has a more efficient solution that was already widely used.

With respect to your particular question - to some degree, this is exactly how original grass fields were treated. But no matter how convenient, there's always a need for consistency and predictability and you can see how that has developed to what we have now. Taxiing a heavy airliner isn't a trivial task - doing so with no markings or defined route sounds terrifying.

Additional practical issues of your large slab of concrete vs. a defined runway:


No ILS
No runway lighting
No runway markings
No threshold, no touchdown markers
Far more difficult to precisely define runway length
Very very difficult to accurately describe a particular location and route


To be honest, the list goes on and on and I'd struggle to imagine commercial ops being able to operate like this safely and efficiently.