Because I work as an engineer for a bearing manufacturer, and I see many manufacturers of transmissions, differentials, and transfer cases subscribing to the troubling trend of going to fill-for--life fluids. I see what happens to these bearings after testing. They don't last long.
These applications have some of the dirtiest, debris-filled lubricant charges, and I see the bearings fail from debris denting after testing. Manufacturers are now asking the bearing people to step up the materials used to make bearings, which have been made continuously from 52100 steel, and are otherwise continued to be made from this steel.
Also, the engineer that handles the bearings for CVT transmissions told me that these bearings are not serviceable at the shop level. They need to be replaced at the factory.
I'm a firm believer that fluid should be replaced after break-in to remove the debris that is generated during break-in. The fluid maintenance schedule should then be continued to replace the fluid that has broken down from shear and oxidized from heat.
I will continue to replace the fluid on a timely schedule, because the $100 I spend on a complete fluid exchange will hopefully allow the transmission to last the life of the vehicle and I can save myself the expense of replacing the transmission. I keep my vehicles for a long time.