They use it because it's effective for killing the cancer! So you're right about that. Risk benefit balance.
One side effect that can happen is hearing loss, which is not reversible. I was getting carbo platin which is supposed to be less toxic to the ears, But 6 big infusion doses every three weeks, with taxol, for ovarian cancer. I had no idea that the reason my ears felt stuffy and I couldn't hear well was from that, so I didn't mention it to the oncologist. Only found out afterwards when I went to the ear doctor. Apparently you're a little more likely to have it happen if If you already have some hearing loss, which I did. Mine went from mild to moderate.
I'm telling you because if you have ear symptoms after the first, you will know enough to tell your doctor and maybe they would do something about the second dose. Or not, depending again on the risk benefit analysis.
I've been in remission for 2 years after finishing chemo so I'm contented with the result. Good luck!