While it would be much more convenient for everybody if they implemented some extension of the current protocol/formatting, there are some issues with accomplis

While it would be much more convenient for everybody if they implemented some extension of the current protocol/formatting, there are some issues with accomplishing that. Names registered with namecoin have to depend on some blobs which can be updated by the name owner. The blobs need a format of some kind, and since they're already using a different protocol than DNS to achieve this P2P system, they might as well use JSON. Also, as I stated in my comment, the structure of JSON fits better for this type of system than DNS's formatting. DNS requires redundancy to describe round-robin, and it's not easy (or elegant) to express complex structures in DNS, compared to JSON. One example of this in practice is the I2P field I mentioned before.