CPUs are ubiquitous. They're everywhere. Anybody being able to participate in mining with general purpose computing hardware is hugely important for decentralization. If the mining algo can be paired down to a specialized chip you will always end up with a situation where a few large players with the most CapEx to put in are negotiating deals with the few producers of these specialized chips to buy large production lots before anyone else can get their hands on them. With CPUs you're competing with the entire computing market and all it's other use cases.