...manufacturing productivity and quality test
Fixture reliability is directly related to three main issues: a clean factory environment,  a clean board production and a regularly fixture maintenance procedure. Failure to deal with these issues leads to a low fixture performance with high rates of re-test, invalid failures of good boards, and in general to low productivity in the test process. 

... and probes maintenance simpler and faster
A typical PCB test fixture includes a fixed plate for carrying an array of test probes to electrically interconnect the test systems to the PCB assembly, and a moving plate arranged above the fixed plate. In a conventional PCB-test fixture the moving plate cover entirely the fixed plate.