The growth spurt of a technological advance - like the tech advance, the production line - etc - may not happen due to capital availability.
The point to keeping money growth at a set level is to cool off exhuberance or even make sure that it either doesn't happen at all or at least doesn't get out of hand. When it gets out of hand, sure some people make out like bandits, but most people don't--most people, especially those who can afford it least, tend to lose a lot of money. They jump in at the top. And that creates bubbles which may be fun for awhile but ALWAYS have bad ends and badly distort economies. It isn't worth it for society or economies, seen from a macro responsible perspective.