Why do mathematicians use single-letter variables?

I have much more experience programming than I do with advanced mathematics, so perhaps this is just a comfort thing with me, but I often get frustrated when I try to follow mathematical notation. Specifically, I get frustrated trying to keep track of what each variable signifies. As a programmer, this would be completely unacceptable no matter how many comments you added explaining it: float A(float P, float r, float n, float t) { return P * pow(1 + r / n, n * t); } Yet a mathematician would have no problem with this: $A = P\ \left(1+\dfrac{r}{n}\right)^{nt}$ where $A$ = final amount $P$ = principal amount (initial investment) $r$ = annual nominal interest rate (as a decimal) $n$ = number of times the interest is compounded per year $t$ = number of years So why don't I ever see the following? $\text{final_amount} = \text{principal}\; \left(1+\dfrac{\text{interest_rate}}{\text{periods_per_yr}}\right)^{\text{periods_per_yr}\cdot\text{years}}$