There are many reasons why. One reason that stood out to me was that there is a barrier in connecting all external components to what the main component ( in this case an aircraft). It not only comes down to if the system itself can adapt to these changes, but if it can relay the information to ground control and air traffic control. I have learned that it will take a more standardize approach in order to see it happen. That being said, the industry is open to utilizing a new approach, but the need for testing and validation is important.