Based on the description on their site, the controller includes a built-in battery: "8.39 Wh Li-ion battery, 35+ hours of gameplay... "
That was disappointing for me. Specially condidering the Steam Frame's controllers make use of AA batteries: "One replaceable AA battery per controller, 40hr battery life"
AA Batteries might not be as convenient to use, but being able to replace them is a great advantage. All my Xbox360 controllers still work fine, but none of my PS3' Dualshock 3s.
The official docking station could be used to recharge (rechargables) AA batteries so the functionality could remain the same.
They said that because you said "I'm not going to buy a 100 pack of rechargeable batteries" because that's a ludicrous idea for a typical parent. Families have two kids on average (trending downward) so how many toys do you think each kid has that requires batteries? How many battery powered toys are they actually using at a given period? Can they share toys? Can you teach kids to charge their batteries and move them? You read into it and didn't even figure out what or why they were calling you out.