Besides, how often are you using your iPad, while constantly using data, for three hours in a row, while not being near somewhere you could plug your phone in? I know it's an inconvenience, but how often would you run into it?
In my day to day usage, not often. At work I could have the phone sit on a charger and provide data. The biggest time I could think of would be when I travel, and I have been in airports a lot more recently with trips back to Colorado. Having recently been able to shed a lot of travel gear, I'd hate to have to go back to being one of those poor huddles souls in the gate area, desperately searching for a spare plug to keep their device charged while using it. My first flight with the iPad was so nice when I didn't have to worry about batteries and was still able to use the device for various streaming while waiting.
The other time will likely be during this summer as Mustang events become more common. Then I suppose I'd have to carry around a charger cable too.
Where is that amazing battery tech we clearly need to just fix this situation? Even Apple's attempts in the area aren't anything new, just highly optimizing existing tech or space.