This is important for PC gamers because PC is the most superior and powerful platform ever. Why should we have to purchase a stripped down version of the game for Consoles, when we can get the full experience on PC? We also have people creating mods, texture packs, etc that only make the game better and more fun for those who like getting their creativity on and it inspires game development which could potentionally increase the gaming market. And it is only fair to release it across all major platforms such as PC, PS3, Xbox 360 (And maybe Next Gen consoles).
If we were not able to receive this on PC, the sales would drasically decrease as though if you subtracted the GTA IV sells for PC from the Console Version.