If interest rates are very high, in contrast, only projects with immediate payoffs will be worth doing. There are many different kinds of projects to invest in. PDV calculations can be made for all of them. By investing, people make resources more productive. But there is an important distinction between private and social returns from investment.
Many people see invention as a case where social returns exceed private returns.
The inventor of penicillin captures only a small fraction of the total benefit created, leading to under-investment in such inventions. Government subsidies could conceivably correct for this problem, though they often redirect invention in unproductive directions. Many see education in the same light, though it's unclear why. Others, including me, see education as an investment where social returns are much less than private returns. If education serves as a signal rather than increasing worker productivity, there is excess investment in education.