I love using a delay with my vocals, even a bit more than reverb in some way. But depending on the type of song I’m mixing, using a delay can be distracting. This technique helps me bring my vocal delay more transparent in my mix. So this way I can add more of that effect without being too distracting.

This technique can also work on other sources than Vocals.

Here is a good article related to this topic from my good friend Tosho at Mixing Tips.
“Adding Delay on Vocals: 4 Basic Types of Delays used on Vocals”