Why aren't more Transformers figures cast in metal?

The first transformer I ever saw, was a die-cast Jazz, and it was awesome. The engineering / design blew my mind - that they had pulled off a convincing car model and a relatively convincing model in the same robot. It was heavy, solid and shiny.

This feeling is lost in the plastic models, which I understand is quite common even in the modern studio series. When a kid can get a pretty functional metal car for $3, it feels very McDonalds surprise / "Kinder eggy" with these plastic toys.

The reason why I lost interest as a kid early 90s was the increasing plasticlike look and feel of the later gen stuff. It's really strange to see it has persisted.