Why Guinsoo's Rageblade loses attack speed when built?

It is really weird, as far as I know items should never lose stats when completed. I remember a while ago, when people complained that a fully build would make you lose AP (or armor, I don't remember) because the components together had more AP than Zhonya itself. There was also a Twisted Treeline-exclusive item that had the same problem, and I don't know if it was fixed.

I get that Guinsoo's Rageblade recovers that attack speed when you stack the passive, but then wouldn't it be better if it didn't had an attack speed item on its recipe to begin with?

Oh, and before someone says that the double on-hit effect passive is broken? It technically is broken. However, it is balanced out by the fact that Guinsoo is incredibly expensive, is not cost nor stat efficient for many of the champions that could potentially build it, you lose attack speed when completed, and you have to stack it. This item cannot be compared to Sated Devourer, which gave you a lot of attack speed to complement the double on-hit passive, didn't had to be stacked, was always up, and came with an on-hit effect itself.