Because you extract most money from the market if you have products at a range of price points. If you only have good expensive products you only get money from rich people. If you only poor cheap products you get money from everyone but not a lot. If you have both you get lots of money from rich people and some from poor people. It's called price differentiation.

The reason they make their cheap product by crippling an expensive product, is because it is cheaper to do that than to manufacture an entirely separate product.