This has to be the biggest question I’m asked daily.
Here are some reasons
1. Your contractor simply underbids the project and there simply isn’t enough money to finish the project they started. So they leave you in a hunt for another contractor.
2. They just bit off more than they can chew. This a very common in contractors.
3. They used your money to pay unrelated bills of their own and they can’t ask you for more so they leave to the next poor soul.
If this has ever happened to you, you should call your local building department, law enforcement right away. Don’t let the contractor tell you anything different. Your money, your house and you want it done.
Also, read my “Payments To a Contractor” before you do anything.