I already said this at least 2 times, but let's try it again: tablets (and smartphones for that matter) typically don't run anything which even remotely uses all their hardware to its full capacity. For things like web browsing or watching a video, 95% of the time both GPU and CPU idle.
If you were to run an optimized game making full use of the hardware using a low-overhead software layer on a tablet, it would
- Clock down significantly from its maximums almost immediately.
- Certainly not achieve anywhere close to the battery life you get in standard tablet tasks like browsing the web or looking at videos.
But that doesn't justify anything:
When people buy an iPad, they plan on doing mostly things that won't be too hard on the hardware, this is the planned use of this device and how it's marketed.
The fact that their battery goes by quickly if you play demanding 3D games is a drawback but not one that "breaks it" on the eye of the consumer, simply because it is not the usual intended use.
The Nintendo Switch primary use is playing these demanding 3D games.
That said, it's a major drawback to the system if its primary use, and what it a marketed and sold for, only achieves 3 hours of battery life.
Comparing iPads and the Switch is irrelevant to me, they are two very different devices aimed at different markets.