You shouldn’t! Tests provide part of the picture; interviews, for instance, provide information tests can’t reach.
But research shows that interviews, references and application forms are very bad at predicting whether people will succeed. Interviews are particularly dangerous because you will be hugely influenced by your prejudices, likes and dislikes without realising it.
If you think back, you will remember the great candidate who proved top be a complete disaster. You might even recall the exciting company which employed you and which you left as quickly as you could. Let’s not forget that recruitment is two way!