That's besides the point. Dedicating yourself to a single item like that isn't fun. Or rewarding. Starting out in Industrialcraft was fun. Copper, tin, and iron, were all necessary starting ingredients, but you would find them all while exploring the same caves. Even once you went to go look for uranium, you could still use those metals. Not to mention redstone, gold, and lapis. Industrialcraft is built intelligently, in that acquisition of new materials usually resulted in opportunities to gather more lower-tiered materials along the way. When you grew out of using coal as a fuel, you started using it as either solar panel material, or to make carbon fiber plates.
GregTech is not built nearly as intelligently. Aluminum dust is an extremely common byproduct, but aluminum ingots have very few uses except to replace refined iron- but when I first got the ability to make those ingots, it was difficult enough to make them that I didn't want to use it for anything other than the things only it can do, which is, basically, batteries. And once it becomes trivial to make aluminum ingots, I'll have more than enough iron, so what's the point? Chrome and titanium are even worse. They're essential for a bunch of machines, but only ruby dust and bauxite produce them, respectively. It was time-consuming and laborious to produce my first matter fabricator, but Greg got rid of the only thing that made the mass fabricator special (iridium) and replaced it with expensive ways to get things I could get by exploring. And the technological leap to the next useful machine is so great that I might as well not bother.