If every employee gets a positive evaluation, then what is the purpose of the evaluation in the first place? Without variance in data, we can't really draw any conclusions about what data means. Yet often in the workplace we value consistency so much that we drive variance out of key measures. This defeats the purpose of getting the data in the first place.
The desire to tell a certain story through our data can lead us to manipulate results and create a misleading picture. Don't let the pressure to succeed overwhelm your commitment to understanding the world as it is.