Think of someone in your life that you know very well and you're sure would never commit a violent crime. Then imagine that there was a violent crime and that LE releases the info that a suspect in the case may have been wearing a John Deere cap. You know the someone in your life has a John Deere cap... but you're still convinced of that person's trustworthiness.
I don't know about you but I know for me, it would be a really difficult decision to turn that person's name in to LE. I also know I'm not alone in that. For instance, Ann Rule made it clear in The Stranger Beside Me that once LE started looking for "Ted" from Lake Sammamish, she found it really difficult to turn his name in.
She did turn his name in but she didn't do it through the tip line. She spoke to a police officer she knew so she could explain how unlikely it was that the Ted Bundy she knew was "Ted."
Ann Rule wasn't the only person who found it difficult to turn in Ted Bundy's name. His girlfriend at the time tried to do it three times anonymously before she finally was able to do it in person. With the benefit of hindsight, his GF's hesitation seems strange because she knew the ways his schedule coincided with the disappearances, she knew he had plaster cast material, etc. At the time, though, it wasn't clear at all. After all, she trusted this guy so much that she was sleeping with him.
I think LE is hoping that if there is someone with doubts out there, that they will share those doubts with the tip email address. I think the email address is ingenious because it is sometimes easier to write something down than it is to say it out loud.
Personally, I don't think the perp currently lives in Evansdale. I think the perp lived there and has moved away but not very far. I could easily be wrong, though.