It's the airport. They don't want to increase their infrastructure costs.
It's the airlines. They will want to figure out how to charge for outlets.
It's the wifi providers. How do they know the people using their outlets are wifi users?
A couple of years ago I ended up doing a conference call in the Las Vegas airport on the floor behind a staircase next to a Starbucks because that's the only outlet I could find at the moment.