Pretty sure that comment was future-thinking, not talking about the technology as it exists today. That is, in an eventual future where you can stream video to a regular-sized cell phone from a satellite, it's potentially a lot cheaper and easier to just throw more satellites in space than to build more towers on the ground. The "holy grail" mobile network would, after all, be that your phone just works from anywhere on the planet, at the same speed, and without need to lease any land or pay for any additional hardwired network infrastructure, electricity, or physical maintenance.
Emphasis on "potentially" since it's absolutely possible that no matter how good the technology is it'll still be cheaper to increase bandwidth to a tower in high-density areas than to pay for more space junk due to the physical limitations inherent in a satellite launch and with satellite maintenance.
Upgrades would also be a question, since the only way to upgrade your thousands of satellite constellation is to launch thousands more entirely new satellites, instead of sending a technician in a truck to towers in major areas first then work your way down to the rural ones. If you don't upgrade all the satellites, then your connection is only as good as whatever is over your head that particular minute whether you're in downtown New York or rural Idaho.