DLSS reduces the VRAM use though and tbh by the time VRAM actually hurts the performance of the 3080 it will probably be obsolete due to other factors anyways. Worst case scenario if you want to run the 3080 for 4 years etc you'd be looking to reduce some settings *shrug*
DLSS is only available in certain titles and requires support from nVidia to implement. I am not saying 10GB isn’t enough, it’s just on a card targeted at 4K gaming they are being very stingy. The other consideration is the effect on memory bandwidth of a narrower memory bus.