Question

explain why some firms want to use longer depreciation periods

Answer 1

Depreciation is an expense which is charged to Income Statement over the useful life of an Asset. By this firm is able to allocate funds for the replacement of Assets after its useful life gets over.

Some firms wants to use longer depreciation periods or you can say longer useful life because:

Management of the firm wants to inflate profit (by decreasing depreciation expense) to improve their performance and get remuneration/ incentive based on such inflated profits. Management may also do this to distract stakeholders of the firms like shareholder, suppliers, bondholders, etc. from actual performance of the firm for their personal interest.