Why big companies are always preferring Experienced people to hire and not an fresh graduate?

There are many reasons :

a) You don't need to train them.

b) They value the job culture.

c) They know how to get along with the team.

d) They know what they are hired for and delivers on time

e) Too many things need not be explained to them as they have gone through the process earlier.

f) They add value to the business with their previous experience.

It also affect's adversely, difficult to groom and change their mindset , raw is better for moulding than hard and firm with experience.  

Because the employee with experience will benefit the company faster and better than the modern era graduation employee