This depends. There could be policies in place per the mortgage or per the insurance policy that the property must be in the same state of quality (or better) as it was when the policy was written. If so, then it is your obligation to return the property to pre-loss conditions. There are also some policies in place per mortgage companies that require a licensed contractor to complete the repairs. In any case, if there is an insurance payout, the carrier has a right to request receipts to substantiate the payout they make for repairs.
One thing to consider if you don't repair is that if in the next few years you have a new issue that causes another insurance claim, they may decide not to cover it because they already paid you to repair the property, and it is your fault that it wasn't. That might also mean they don't pay you for the stuff that is damaged because of the "new" problem.