Because for a long time, shortages did not matter except to control prices. So everyone built FMU, electric power, oil, and a few other things I don't remember. The GMs sculpted the economy on these lines to match because "everything was going great".
Then they decided on their world specific products and weakened the process that held things in magical happy supply land significantly. You saw how effective it was in the past, there were no shortages.
So they pulled off some of the stops, made the handouts less, and now we might be heading to what could be called a real economy, circa 2003.