I don't understand why people are trying to build smaller PCRs. Why PCR of all things? You can do close to nothing with PCR alone. You'll need primers, enzyme

I don't understand why people are trying to build smaller PCRs. Why PCR of all things? You can do close to nothing with PCR alone. You'll need primers, enzymes, buffers, centrifuge, electrophoresis instruments, etc PCR is not an expensive device compared to all the other costs of experiments.