Why the position or Salary not updated when moving to an internal candidate to HR?

Hello, excuse my English.

Recently it has happened to me that recruiters create an offer for an internal candidate with a position, carry out a transfer or promotion action and when the candidate accepts it, it goes to HR without problem.

but when searching for it in People Management, the position is different from the position in the offer, it is not updated, the worker it remains with your previous position. And other times the salary is not updated.

 Does anyone know why this happens? Thank you.