Why?
In 2012, around the time of ps4 release everyone said 2 GB of VRAM is ALL you need. It very quickly became a complete necessity about 3 years in. Then it was 8gb of ram, now 16 is almost a complete necessity. It goes on an on, if you want your computer part to run high/ultra for the next 3-4 years I would always go more VRAM if that was an option.