Why are employers hiring younger and inexperienced candidates as opposed to older and much more experienced personnel?

Young and inexperienced candidates are quick to learn, they don't demand higher salaries as compared to experienced candidates,they are easy to incorporate when it comes to multitasking and are able to adapt to modern technology with ease.

to pay more less salaries and reducing the salaries balance costs 

also the employer see that younger candidates  more active and have goals need to achieve it so he will work more than the elder.

They stay longer.

have Less demands.

This is a nice question! i think, companies tend to hire inexperienced and younger candidates because new entrants focus on learning and are more likely to stay longer and demand less, despite of the fact that HRD section invests more in new comers than in experienced ones.

Younger and not good qualified ppl, don't complain that fast. They are afraid about the working certificate or if the candites are queing up in front of personal door. What would you do in that case.

Sometimes experienced people shows their high range of fatigues  and also some jobs requires more energetic and young people while they try to learn from what they are doing to gain experience.Opportunity creates experience so the freshers are like a blank paper where you can write any module according to your requirement and let them work according to the business need and call.The younger and freshers always fears to loose their job due to their failure but the experienced older people always looks for more opportunity to move to the new job and somehow they are stubborn and proud due to their experience and age. 

Mainly for cost saving.

Experienced specialists are very expensive and since programming languages are becoming more simpler in our days it is easy to learn them then it used to be before our time.

INNOVATE BY TAKING RISK

THE NEED FOR MORE LEADERS

CURIOSITY TO LEARN NEW THINGS

Some jobs needed for younger and fresh blood like call center . For health and psychological reasons the call center agent most leave this job or change the task within 1 or 2 years maximum. also for cost issue.

but there are fields needs experience like accounting , engineering ...etc

Each company has it's own internal politics and set ways. The less experienced you are, the more eager you are to do things the new employers way, except and learn.