It's not about require, it's "more better".
IEMs are not generally hard to drive but having more power at low volumes makes a difference sometimes. I was convinced to bite the BTR17 after listening to a buddy's BTR7, and it's surprising to me that the BTR17 delivers slightly less power than BTR7 when not in desktop mode. Although it's not very fair to do that comparison, since my recent portable squeeze is the Onix XM5 and that thing is a monster with a background black as night and so much power on tap even in medium gain.
BTR17 sounds very neutral across the board and I like it very much with Trailli. I need to check a bunch more IEMs to see if the complaining someone did about it making all IEMs sound similar is accurate.
Then again, I wouldn't have bought this if Fiio had made a better UTWS5 for 2025, so...