But it does go to equity. The lease payment is made up of depreciation and rent. Depreciation is the difference between the sale price and the residual and rent is basically interest on the prinicpal portion. You can determine the implied interest rate in excel very easily with just the rate function using sale price, residual, term and payment.
You are paying down the principal to the residual with each payment. Now if you think the car will be worth less than the residual at the end of the term, it is probably worth leasing and buying another (or the same) car at that time and at market rates.