why it takes so long to get covid 19 test back code example

Example: how long does it take to get results from covid test

I got results back within 4 days from MAKO. This is what is says,
  
Negative (Not Detected)
The SARS-CoV-2 test is intended for the 
presumptive qualitative detection of nucleic acid 
from SARS-CoV-2 in upper respiratory specimens. A 
Negative result does not exclude infection caused 
by SARS-CoV-2 and the results must be correlated 
with clinical presentation and evaluated in the 
context of other laboratory and epidemiologic 
data. 
The COVID-19 RT-qPCR test is a Laboratory 
Developed test (LDT) not approved or cleared by 
the FDA and has been approved for Emergency Use 
Authorization (EUA). This test has been authorized 
by FDA under an Emergency Use Authorization (EUA). 
This test is only authorized for the duration of 
time the declaration that circumstances exist 
justifying the authorization of the emergency use 
of in vitro diagnostic tests for detection of 
SARS-CoV-2 virus and/or diagnosis of COVID-19 
infection under section 564(b)(1) of the Act, 21 
U.S.C. 360bbb-3(b)(1), unless the authorization is 
terminated or revoked sooner.