It's about having a consistent measurement baseline. Say you run your benchmark once, then thermal throttling kicks in, then you run it again, and it takes twice as long. Is your code actually slower now? Should I wait until the fan turns off before I run it again? That data is noisy and useless. Take your measurements on a server or desktop with sane thermals and a full-size fan.

If you speed things up by 10% on your server, they'll get 10% faster on your laptop as well.