Interest rates today are lower than they were when you took out the home loan.
Your credit score has increased.
Your DTI ratio has decreased
Your income has gone up or down.
You are eligible to remove MIP or PMI because you now have sufficient equity.
You want to pay a lower amount each month on your mortgage.
You want to change your fixed rate to an adjustable rate or vice versa.
You want to borrow funds for home upgrades and repairs or other expenses.
You have debts to consolidate.