Yeah it's always annoying, although you pay the price for that VRAM. But 10GB should be enough to play in 4K with all details, having a bit extra would be nice (12GB or 16GB), but I don't really see the point of 24GB, for gaming at least.
The 3090 is targeted at AI ie, deep learning..., if for gaming 24gb makes no sense, not bad to have but no point in having for games that amount right now, 16gb should be the normal for 2020, 2016 was 8gb, only 16gb makes sense for a flagship like rtx 3080 in this time and age. It seems micron is having a hard time to produce enough gddrx6 for it, they dont want to sacrifice the ones on 3090 and want the 3080 to take the hit, I guess the 3090 has a higher margin of profit, so the good gddrx6 memory modules will all go to 3090 and the leftover to 3080. I guess nvidia will launch a 3080 super later on with 16gb once things get to hard mass production at micron factories.
monitor size, screen resolution plus other graphics quality config on PC games tends to eat a lot of vram, my 1080ti 11gb ram gets filled when i max out game settings with my 24 inch 1900x1200 resolution..having ~34 inches monitor will need that 16gb at least, 3080 "10gb" is a teaser, gamers will hate that later on.
1080p gaming is dead, when i played new dawn of far cry, in the hazy/hallucinogen part of the game, the difference with 1080p vs 1440p and 4k with enemy visibility is huge.
10gb of vram for mining, i think it will be fine for quite a long time unless there is some algo tweak of new algo that will hash a lot more when more vram (greater than 10gb) is utilized.