Speeding up part of the problem while largely ignoring the rest leads to diminishing returns. O speed does not matter in a multiprogrammed environment. If a process waits for a peripheral, run another task. This is an argument that performance is measured as throughput and response time does not matter. This is hardly the case today with desktop computers running interactive software.
Response time is directly related to productivity.
Storage devices Storage devices are mechanical , so they are subject to real physical limitations. A disk made of any material that we know of today would fly apart. These mechanical delays are far more difficult to eliminate than electronic delays. Reducing the size of mechanical devices is more difficult than reducing the size of electronic circuits. Automated tape libraries.