Why do companies find it difficult to employ good people?

Now I'm only young, but in my common sense i should think that possibly the people who are interviewed for a certain job and have a lot of experience and are good for the job, companies think that they can get any jobs they want easily. So they employ the ones who will probably have difficulty finding a job and desperately need one to feed there families and pay bills and depts because they feel sorry for them. Actually I'm trying to sound all 'intellectual' and all that stuff whatever, im just saying what i think u no? :)