Someone who has worked for your company for a long time probably now has a significant knowledge and experience of the industry you are in, as well as the services you provide or the products you sell very well. Instead of retaining these people, transferring employees from a larger or prestigious company outside the industry is like exchanging your gold for silver.
Remember; The cost to the company of a staff member leaving the job is up to 2.5 times the annual gross wage of that person.