The reason behind such big time technological companies being invited? Business interests from the various parties have certainly piled a fair amount of pressure on the FAA and Congress where wider drone use is concerned, although there are fair worries about public safety and privacy.
Eventually, there is the possibility of enabling the use of a wider array of drones over public spaces, which will certainly be in the favor of companies that perform drone deliveries, but also to those who manufacture and sell drones to recreational users. Right now, drone owners will need to register their drones with the FAA (for free) and so far, the number of registrations have been encouraging to say the least.