Why do employers always reject adult job seekers without any further selection , even though they are still competent and healthy ?

Is because some superior managers, are selfish and don't what the new worker to get an experience in order not to take the position if worker is exposed more in the job 

Teamwork is one power and integration that complements one another (one hand does not flow)

they tend to have a fixed mind in how to handle a particular problem and may not be open to new adieas