The primary reason she continues to behave as she does is down to the media continuing to report on her. In her delusional mind, if she's getting attention - and she is, continuously - then she's doing something right, and for someone like Lyndsay, that's all that counts. Her mother is her main problem, as deluded as Lyndsay but cunning with it and her daughter's chief enabler.
I think a lot of Hollywood genuinely feels sorry for her and wants to see her make a healthy comeback. Unfortunately, as long as her mother is there to validate everything she does, nothing good will happen for her. I don't think jail would make one ounce of difference. I don't think rehab would either since rehab only works when you acknowledge you have a problem and Lyndsay doesn't believe she has one. I actually feel really sad for her.
This recent interview with director Paul Schrader pretty much sums up her mindset - here is what happens when you cast lindsay lohan in your movie