I find that most performance reviews are designed to deny raises in order to cut costs and live within an allotted salary budget.
It's especially bad when a stellar team is evaluated and managers "have" to find fault where there may not be any. They are compelled to grade using a bell curve. Managers are encouraged to "ding" employees to prevent them from getting high "scores". I've seen several performance evaluations where even if top marks were given across the board, the employee would not have enough "points" to receive the top level raise bracket. Managers have also stated during reviews that they aren't "allowed" to give top marks. Its unfortunate, because excellent employees leave feeling unappreciated and with a "why-do-I-even-bother" attitude.