It’s not about money only. When we create something, we would like it not to go down the sink too quickly. Sure nothing lasts forever, but if what we create shows to be useful for as long as it can, all the better.
How to do this when technologies crop up as quickly as mushrooms after a rain storm and disappear as quickly?
Software development is about problem solving. It isn’t about technologies.
When you write a piece of software, you are describing a way to solve a problem.
If you document it well and your description of how to solve a problem is clear enough, when you have to change programming language, framework, libraries, or need to use the newest flavour of JavaScript, you have documented solutions that you can reuse.
You don’t need to throw everything away.
A well-documented and well-structured software not only is easier to modify, adapt and troubleshoot. It protects your investment because it documents a solution that is technology independent.
When you switch to a new technology, that solution comes with you.