It's basically Parkinson's law. If you give someone 10x the performance, they'll find a way of doing the same things they did before using 10x more resources.

It's why you have user interfaces today that are often as slow as, or slower than the equivalent Windows 3.11 interfaces. In 1993 things took time because the processor was an actual potato and the data fetched off a floppy disk, today things are slow because the code being run is 1-10k times slower and messages need to be continuously sent to a datacenter half way around the world to inform an analytics server about your every input.