Lenders typically ask for a depreciation schedule if you own an asset, such as investment real estate, that generates meaningful depreciation. Lenders consider depreciation a passive expense, which means it can be added back to your income to determine what size mortgage you can afford. Adding back depreciation to your income typically improves your ability to qualify for a mortgage or enables you to afford a larger mortgage. Please note that lenders usually only add back depreciation that is attributable to long lived assets such as real estate. Appreciation that is attributable to shorter-lived assets, such as piece of machinery, are not typically be added back to your income.
In most cases, providing a depreciation schedule to a lender benefits the borrower but I recommend that you contact your lender to determine the reason for the request.