Hey guys...
buze,
Its also about striking a balance. People who use on-board graphics are not usually the ones with serious performance requirements. Those who are buy a dedicated GPU. Going from 512 > 1024mb memory allocated for on board video is not going to yield a substantial performance increase or FPS.
Please also note that not everyone installs greater than 8GB of RAM. While the minimum memory requirements for most OS's remains low, we know from experience that anything less than 8GB on a x64 based system can be performance limiting for anything except email and casual web browsing.
So to avoid bottlenecks and maintain equity, lower memory allocation limits are established. If a user wants more, he/she can buy a dedicated GPU and it becomes a mute point. Shouldn't be a deal breaker for you.
Cheers