Answering this question is a pain in the ass and frankly it’s basically the same reason why people hire me. Sadly the #1 reason is that after 35 years of progressively more difficult projects I have a fine tuned intuition about these things. Some of the reasons give are very similar to the reasons Hipp gives.
Hipp gives reasons for Fossil (version control) too. The fact of the matter is that generally WE work on small projects. The complexity of all things will cost you specially when you commit to those costs early. You are better off with a simple design that can be modified on the fly.
I’m not going to say any more for now.