Ask HN: Why do companies issue crappy machines to developers?

Companies are willing to pay big money to developers, however they issue crappy laptops as development machines. Laptops are designed for mobility, not for performance. Sure, you can use a dock and plug a keyboard and external monitor(s), but a Core i5 laptop with 16GB of ram running at 1.6GHz won't cut it as a dev machine. I would imagine that companies would want to provide the best tools for their developers so that they can be happy and productive. What is the rationale for companies to do this kind of short-sighted thing?