As I understand it, DEET just prevents biting as they don't like the taste of it, and they taste with their feet. Thus, it doesn't do much to prevent initial attraction.
Edit: thought I'd include a link to a study about this as it's not well known. https://www.cell.com/current-biology/fulltext/S0960-9822(19)...
I believe DEET interferes with their ability to locate prey actually.
There may be multiple ways it works, but we don't fully understand all of them. However, here is one study about the feet to show I'm not spouting AI generated bullshit: https://www.cell.com/current-biology/fulltext/S0960-9822(19)...