The external hard drives that we have seen and tested are like ours where if the hard drive is connected first in the chain, it must remain powered on to allow the other items in the chain to work. Thanks for the question!
If you look at our competitors, Rocstor, G-Tech, LaCie, etc, they do not include fans but feel the metal enclosures are enough to keep it cool. For the most part it does. However we feel for our customers that are using every bit of bandwidth on these interfaces that the addition of small fan to keep the air moving around the drive is beneficial and sufficient. Email us if you have further questions.