Answer 1

With the technology we have today, each core of the CPU is able to process something. So it's a combination of being able to process multiple things at the same time, as well as the processors being quicker than they used to be. With threads (multi/hyperthreading), you're able to take a single core and divide up the tasks on it so that you essentially are able to do multiple things at the same time with a single core. When you compound that with multiple cores, you're only increasing its ability to do so and thus increase the performance overall.
Hope that helps. Once upon a time your statement was true and we weren't able to do that. Those days are long gone tho.