These are all filtering devices. You can debate their relevance or accuracy until the cows come home. Supply and demand determines the application of filters to reduce numbers.
A similar but different example. Emirates would only take pilots with jet experience above 50 tonne MTOW. Next minute they were hiring turboprop pilots.
Supply and demand.
Some airlines in Australia currently use the mirror test. They place a mirror up to the applicants nose and mouth, if it fogs up, they have a job.