Smaller transistors bring everything. They have lower resistance and capacitance resisting a switch, you can build more of them at the same time (so, approximately by the same cost), a signal takes less time to pass through them (and to get from one to another), and they have a larger surface/volume ratio for cooling down.
That said, transistors actually stopped shrinking a while ago. They are getting packaged nearer to each other, they have changed from horizontal to vertical, and they are changing the width/length ratio, but they are not really shrinking.
That said, transistors actually stopped shrinking a while ago. They are getting packaged nearer to each other, they have changed from horizontal to vertical, and they are changing the width/length ratio, but they are not really shrinking.