Why?

Weak pretests discourage guessing.

There are many contestants who only have a faint idea of why their solution works at all. The problem style of recent years has contributed to this. If the solution boils down to "check this elegant condition, answer YES or NO based on that", then it is very much possible to solve problems by guessing. Especially with full feedback.

Remember 1375C - Element Extermination? The solution is to check if $$$a_1 < a_n$$$. Tons of people under the contest announcement were excited to explain that this is how to solve the problem. Only a few could explain why it worked.

This is also a situation where it is easy for a high-rated author or coordinator to deceive themselves. If you already know such a solution, then it may seem very easy. The implementation is easy and if there is a clean observation you have to check, making that observation seems easy in hindsight. And the large number of solves in the contest "confirms" that it is easy. But in fact, the problem is only easy to guess, not easy to solve.

In the good old days it was not seen as a big violation if pretests were weak. It was normal. Right now weak pretests cause an uproar because people are not expecting it. If weak pretests were the norm, it would not be such an issue.

Make weak pretests the norm again. It will improve the quality of standings.