Complexity of index calculus method

Question

I read somewhere that complexity of index calculus method which calculates discrete logarithm over $Z_p^*$ is $O\left(e^{(1 + o(1))(\sqrt{ln(p)\times ln(ln(p))}\;)}\right)$.

My question is, why don't we write $(1 + o(1))$ as $o(1)$ in exponent?