exp and log not being evaluated

I have a function in matlab that is defined as :

 syms y b
 f(b,y) = (exp(b)^y)/(exp(b))

I have a variable bucket that stores repeated multiplication of this function. Everytime, the function is evaluated at a different value of y, equal to the loop counter.

 for counter = 1:10
     bucket = bucket * f(counter,b)
 newFunction = log(bucket) %thus the new function has only one parameter b

Then, based on certain manipulations, i find the value of b that should be used in the bucket. So, I do

 subs(newFunction,b,foundValForB)
However, the answer has terms like exp(constant). Why doesnt matlab evaluate the exp terms?