We didn't? It must be a small minority of countries that dole out the same punishment for both.

This is probably not the place for this discussion, good luck

> I don't genuinely understand why rape and murder are always put together in the same category.

Not always, this is a fairly recent development only occurring in Western culture. The reason is the feminisation of society. Women lobbied to elevate rape to the level of murder in the minds and in the courts, and men helped them to achieve this.