Why do we need multiple test cases?

i am new to uvm , i want to understand why do we need multiple test cases why cant we use a single test , as we can execute our requirement one after the other why make another test ?

In reply to Raghav_Sharma:

Turnaround time.

You can run multiple shorter tests in parallel instead of waiting for one long test.

When your tests are shorter and one of them fails, it will be quicker to debug and validate the fix.