Sigh .. basic economics. You've demonstrated you don't understand basic economics and business budgets. Businesses allocate funding for associate advancement, and this often doesn't include raises for every single employee (at least for medium and large organizations). Performance is often an anchor point to reward, where the associate has added value and advanced the organizational goals / milestones. Why would you reward someone who is just .. average compared to employees that align with the company vision and values, and are .. productive?
You still haven't answered the question .. I'll phrase it another way. If a poor performing associate works for a company for 30 years without a raise .. what forced the associate to stay at that organization? It's extremely common to move to another organization with an outside perspective ... and make more money.