The cynic in me thinks Motorola somehow won't really enable that since it would cut into their recurring sales too much..?

But, I agree. I used several Motorola phones and those were the main two reasons I replaced them. They either ran until the battery was misbehaving or I became concerned about the state of the software. The other reason would be actual tech changes such as LTE/5G and the transitional period where not all models supported all the important radio bands for my providers.

A few Motos have stayed in the family and had amazingly long lives as home devices (no SIM). I'd love for the balance to somehow come out in favor of your hopes. I.e. they decde they can save so much on OS maintenance costs that they don't mind the effect of users holding onto phones longer.