It’s because they know one dissatisfied person leaving is cheaper than either giving everyone a raise or creating 1 satisfied but many angry people after the others were ‘unfairly’ looked over for a raise.

That and for many people/managers it’s just the default to do nothing until required.

That is only true when employees are not skilled and do not gain inside knowledge.

Small business with one person leaving having a catastrophic impact, sure.

Giant corporation, one person can’t tip the scales, regardless of skill and knowledge.