Convenience. I keep one on my desk. Everytime I sit down, I place my phone down on my charger pad, because that's where it goes. The 1 less step of having to hunt for a cable and plug it in makes it second nature to have my phone always charging or fully charged. Similarly in cars that have wireless charging nowadays, there's a tray of some sort to put it in.

Rather than charging when I need to, wireless charging makes it convenient enough to be charging all the time. Unless you have a lifestyle where you're out and about, and you don't have chargers everywhere you are, it's a nice addition.

Also less stress on the physical port. My Nexus 7 2013 has a broken microUSB port that I can still wirelessly charge.