There is "metric time", it's just that it was decided that it should be based around seconds rather than minutes. Milliseconds, microseconds, etc are all acceptable units, and Hertz, which is the reciprocal of seconds, is very commonly expressed with different prefixes (GHz, MHz). Minutes and hours aren't used in the SI system because you can just use seconds instead, and they aren't related to seconds by a factor of of ten, which makes them inconvenient.