Under the reasoning that hiring is expensive and training is extremely expensive?

1. The salary of a current employee will always be lower than the salary of a new hire, even a year later,

2. The hiring process itself costs tens of thousands of dollars,

3. A new joiner is useless for 2 months, needs to be babysat for 4 more and will ask constant questions for 6 more (if not 18). This costs the company a lot in terms of support that has to be provided from more senior (in tenure) employees.