Unlike a PCR test that requires a doctor or lab technician to perform and a lab to process, a Covid rapid test kit (rtk) is easy to use, and can be performed by anyone who can read and follow the instructions in the test kit. PCR test result can take up to 24 hours but an rtk result can be obtained within 15 minutes.
So the rationale for using an rtk is that it is easy to perform and we can get the result quickly. However, rtk pick-up rate is only about 80% at best, so there is still the possibility of a false negative test.
To better improve the pick-up rate, we should repeat the rtk test within 24 to 48 hours after it is tested negative the first time.
Here is an article that explains in greater details.