I didn't have a mortgage loan, why turbotax ask me to input 1098 mortgage interest ?

 The most likely reason the program is asking for mortgage information is that you reported paying mortgage interest in a previous tax year - the program doesn't want you to forget income or deductions you had before and may still have.

You will have to delete any Home Mortgage Interest Worksheets or Form 1098:Mortgage Interest Statements that carried over from your 2016 tax file.

See: How do I delete forms in TurboTax Online?

After deleting these worksheets and statements, log out of the program. When you log back in, use the Delete a Form tool (List of Forms in My Return) to confirm these worksheets and statements have been removed from your return. 

I made sure my Forms list doesn't have a mortgage form... and i've deleted every instance of it... when I log back in, its not there, but during the review phase it adds the Mortgage Interest and Refinancing (Form 1098) and asks me to fill out the boxes. going to the Delete form page, the form isn't there to even delete

Try deleting the worksheet:

1. Under Tax Tools, choose Tools
2. Choose Delete a Form
3. Scroll through your return until you find Home Mortgage and Interest Worksheet and any 1098's, click Delete to the right of the form
4. Confirm that you wish to delete the form