The following story illustrates why capacity management is needed to consider the most appropriate action to improve performance. I suspect you could insert any resource you wish in place of “network” and the assertion would still be valid.
Firms waste billions on network over-design
Who needs desktop Gigabit Ethernet anyway?
It is true that simply upgrading hardware until the system performs well can look like an effective solution in many cases. It can avoid often complicated analysis and testing work, and in many cases will be effective in the short term. Simply continuing to throw hardware at problems as a strategy, however, doesn’t really work. The issue is that solving a solution in this manner will generally be a short term fix. If the solution continues to be to keep adding more resources then eventually the costs stack up to be unacceptable. In many cases there will also be a point of diminishing returns where even the best hardware on the market will fail to keep up. A more informed decision can be made by characterising a system and estimating the capacity that may be required to meet future requirements.