But just as an accounting note: R&D expense has nothing to do with the company having revenues for an existing product, which already is allowed to deduct cost of goods sold, selling and admin expense. It is a cost related to future business and in that regard, it is not crazy to say it should be amortized. That in the past this did not happen, or that accelerated depreciation for other assets is in the IRS code is a function of the government wanting to effectively subsidize business investment.
https://pro.bloombergtax.com/insights/federal-tax/rd-tax-cre...
https://tax.thomsonreuters.com/news/the-future-of-rd-expensi...