Because AMD and NVIDIA are the most upstream chip and public version designers.

Asus, Gigabyte, MSI, Colorful, Zotac, etc. are all downstream specific hardware manufacturers. AMD and NVIDIA produce the chips they develop and then hand them over to these downstream partners. Secondary design and production of specific products.

Some of these brands have their own factories, while others specialize in OEM production and then sell them on the market under their own brands.

Extended information:

Nvidia graphics cards have two series, namely: GeForce (GF series for short) and duLegacy (LG series for short).

The GF series is divided into notebook graphics cards and desktop graphics cards.

The notebook graphics card series include:

GF900M, GF800M, GF700M, GF600M, GF500M, GF400M,

GF300M, GF200M, GF100M, GF8M, GFGO7M.

Desktop graphics card series include:

GF900, GF700, GF600, GF500, GF400,

GF300, GF200, GF100, GF8, GFGO7, GF6, GF5FX.

Baidu Encyclopedia-NVIDIA