If you "need" a 16GB card, great. But we're talking about a 30% performance delta — MORE at 4K than at 1440p ultra. Even with games that can push up against 12GB. Given you can run 4K with DLSS quality upscaling (renders at 1440p), that basically kills off the need for 16GB in most games. Would 16GB be nicer to have? Sure. So would 18GB! (Using 3GB GDDR7 chips.) But right now, "saving" $100 to get 4GB more VRAM but 33% less bandwidth and 26% less compute is a bad choice for nearly all buyers.
16GB is most practically useful right now if you want to run one of the LLMs that exceeds 12GB. That's easy enough to do. It's why the price jump between 5070 and 5070 Ti is so much higher, and even why the 9070 costs $100 more than the 5070 at current online (US) prices.
People love to pretend that there's a "need" for 16GB for gaming, and there's absolutely not. There are individual games that need 16GB to run certain settings, almost always at 4K native with maxed out settings. But that's mostly the placebo effect, because 4K high will look 99% the same and not exceed 12GB.
TLDR: There is no concrete rule on how much VRAM you need. More is better, everything else being equal, but in this case there's nothing even remotely close to equivalence between a 5070 12GB and a 5060 Ti 16GB.