No, conservatives haven’t forgotten that. You just misunderstand what conservatives are arguing.
You seem to be espousing a psuedo-Keynesian philosphy here, which assumes that the economy grows based on aggregate demand (i.e., the more people buy, the more the economy grows). On the other hand, Supply Siders think that what drives long-term growth is the marginal return on invested capital.
Under a Keynesian philosophy, aggregate demand can be increased by deficit spending. So if the government runs a deficit, then the deficit will always be mitigated by the increased demand it creates. And that increased demand will stimulate the economy’s recovery, and can always be paid back when the economy is doing well.
Meanwhile, Supply Siders think that running deficits decreases the return on capital investment. So they typically oppose running deficits because they think it decreases economic growth, even when done during a recession.
RTFirefly appears to have touched on this (perhaps inadvertently) here:
A Supply Sider would hope that your hypothetical rich person would invest the money. That’s exactly what a Supply Sider is counting on.
And lest we forget, jshore has already pointed out that if we’re looking at aggregate demand, then we shouldn’t stop merely at the point of investment. The money that the Supply Sider spent to buy the stocks is now in the hands of another investor. And what’s he going to do with his money? Either spend it (increasing aggregate demand) or invest it (increasing aggregate demand, and providing more invested capital).
Only if by you use the term “inefficient” to mean “not how jshore would spend his money.”
In fact, the efficient use of money implies that it’s going exactly where the market wants it to go. While you might want to funnel more money away from SUVs and into electric cars, the vast majority of consumers do not. So the fact that much more money is being spent on SUVs shows that the market is working efficiently.