Warning: The following contains SPOILERS for the new Halloween movie! Proceed with caution.
If you've seen the new Halloween movie, you know that Judy Greer's Karen Strode has a strained and complicated relationship with her mother, Jamie Lee Curtis' Laurie Strode. That, coupled with Haddonfield's apparent proximity to the psychiatric institute where Michael Myers, the reason for her mother's paranoia, was kept, begs the question of why Karen hasn't moved away. Judy Greer, who plays Karen Strode, imagines the reason is part practical and part optimistic, as she explained:
So often in life, where people live is dictated by their jobs and vice-versa, so Karen and her family stay in Haddonfield in part because of her husband Ray, played by Toby Huss (also known as Artie, the Strongest Man in the World) and their jobs. This is a practical reason and makes total sense, as most people don't just move in a way that goes against practical concerns such as these.
The other reason Judy Greer postulates to Entertainment Weekly is less practical and more idealistic and hopeful. Karen Strode hasn't moved out of Haddonfield because, despite the strain in their relationship and the difficulties of her childhood, Laurie is still her mother. Instead of giving up on her, Karen stays, hoping to someday repair that relationship.
This paints Karen as an inherently good and hopeful person. She is someone who doesn't hate her mother, but just doesn't fully understand her. It's not that she outright doesn't want her mother to be a part of her family's life, it's just that she doesn't want the PTSD-suffering, morbid survivalist who believes in the Boogeyman to be around.
Even though in the film we see Karen purposefully avoiding contacting her mother and not inviting her to family events, this reasoning rings true. Although a person might drive you crazy or be the cause of much pain, bonds, especially ones as deep as mother and daughter, are not so easily severed and abandoned.
So even though Judy Greer's character doesn't appear to be actively trying to repair that relationship, perhaps she is hoping that one day her mother will just get over her pain and fear and when she does, Karen will be there waiting for her.
There are some other factors that Judy Greer doesn't really get into that I also think played a role in Karen staying in Haddonfield. For one, just because her relationship with her mother is difficult doesn't mean she has problems with anyone else or the town itself. She has a life there and presumably friends and other things, so moving because of one relationship at the expense of others doesn't make much sense.
Also, it is important to note that Karen wasn't alive when Michael Myers went on his rampage. He is an abstract to her, someone that is the cause of her mother's trauma and indirectly some of her own, but not something that she has experienced first hand. In Halloween, we see Karen's skepticism at her mother's fears, not viewing the incarcerated Michael as a real threat, so it doesn't seem likely that any proximity to the killer would bother her enough to force relocation.