#1. Effectiveness

Older staff are more productive than their younger colleagues. More mature members of staff may be weaker and less agile than their junior counterparts, but they more than compensate with their greater experience, ability to work in teams, and success at coping when things go wrong.

But younger employees are more creative, and also, in manual  work, they are stronger

#2.Reducing losses

older workers made fewer or less severe mistakes, while younger workers tended to make more frequent and drastic mistakes. It's wasting time when an older worker instructs a younger colleague on how to perform a task correctly and efficiently.

But when learning new things, young employees tend to adapt the info faster, and older employees learn new things in longer time      

#3.Fees for reducing and replacing staff is very expensive

Instead of retaining experienced older workers, companies must recruit more young workers, it needs the amount of unworthy money.

But if you employers don't recruit new employees, temp employers cannot discover pp who are potential for the job and they can't improve their business.

#4. High costs of training new employees

for young workers, to get familiar and proficient with the new job is very difficult. They need to be trained and instructed by experienced colleagues which make the company a lot of time loss and money.

It's the same with training older employees anyway.and those older ones will even take longer time and money to train than the young.