I think there are several reasons for this.
Firstly, simple design places higher demands on developers than complex design. You need sufficient experience and a deep understanding of the business to create a design that is just right. Otherwise, after several iterations, your code is likely to become bloated—for example, a single file exceeding 2,000 lines or a function stretching over 500 lines.
Secondly, I strongly agree with a statement I once read (though I can’t recall the exact source): "Good code isn’t written perfectly from the start—it’s shaped through continuous refactoring. You need to refactor it at the right time." However, most companies simply don’t allocate time for such refactoring, as new requirements keep pouring in.
Under these constraints, it becomes clear that most companies tend to favor complex design as an engineering trade-off. We have a range of tools for complex design, such as SOLID principles, design patterns, and DDD. But there’s little guidance on simplifying design. I rarely see blogs discussing how developers should judge whether a design is over-engineered or what constitutes a just-right design. In such cases, having some design is better than having none at all—after all, many companies truly operate without any design, relying solely on copying existing solutions.