If someone's production does not increase, their worth to an employer, why do they merit an increase?
'Jay' worked as an EMT for a company in town. He was paid a certain amount and worked extremely hard for extremely long hours for 'little' pay. 'Jay's productivity did not increase but he still deserved an increase in pay. The company would not give him any increase...and treated him with little respect.
One day 'Jay' was asked to work for another company ... for more money and better hours. 'Jay' took the job. After several months his old company called him up and practically begged him to come back, offering him even more money and better hours and several other concessions.
It's not that 'Jay's productivity increased - he was already working at a very high level. It is just that the 1st company took him for granted, did not respect him, did not pay him what he was worth...until they realized later just how important he was to their company /business.
...and not everyone (or anyone I know) gets to raise their own salary and give themselves massive perks and bonuses like out politicians do...