What a game uses and what a game needs can be very different. Most games will use more when it available. I do however think 12GB on the 3080 is a better amount, I just think 16Gb on a 3070Ti is more about marketing and pricing
That's a bit of unnecessary semantics in this context, although I do get your point. I cannot tell (and expect) a developer to cap their memoy usage at 8, 10, 12 or 16GB+, or expect a game to cap at any arbitrary value, so I can only talk from what I see the games I have and play on actually use and infer from that, as I have 16GB (6900XT) of VRAM available to measure, they are capped and coded around 8GB, but still going all the way to 9GB at times. The one that's used the most is Half Life: Alyx at 9.5GB, and then VRChat is always hovering around 7.5GB, depending on the world and the texture quality of it.
So, I'm not so sure, in particular, the 16GB of the 3070ti to be a gimmick. Sure, it probably is to any person playing under 4K or not using VR, but these are not "mainstream" cards anymore. And the people willing to spend the shekles know exactly the purpose they'll give to them. I have a friend, who is a game developer, and he needs a 3090 to not only play games, but also develop, for example. If the 3080 would've been a 16GB card, he could have skipped getting a 3090, for instance. And so on. Certainly not your "general use case" and I'll agree (preemtively) there, but given the price range I did expect more on day 1 from these cards. Again, I'm glad nVidia realized this, but I am now wondering if it is truly because of "gamers" xP
Regards.