Single biggest improvement i experienced was moving from a Macbook Pro as my server/streamer to a dedicated, purpose built server/streamer. To give you some idea of the improvement it made, right before I took delivery of the Streamer (an LDMS Mini by Lukasz Audio, which cost me about £6k), I had been loaned a Silver Core Wanfreid Pre Amp (about £20k!) to use in my system, which at that point was simple MBP-DAC (with volume control)-Power Amps, i.e. no pre-amp.
The Silvercore pre-amp was doing amazing, wonderful things. I was quite surprised by how adding something into the signal path made such a vast improvement, but it did. I remember thinking, why would I do this to myself? Just when I should be about to enjoy the upgrade from the MBP to the dedicated sever, I'd be giving back the pre-amp and mourning it's loss. Perhaps a £6k server might offset some of that loss but I'd still be net negative.
Well not a bit of it - the server improved the system by the same order of magnitude as the Preamp did. It was remarkable.
All the devices you've cited (OP) in that list are all terrible sources, as well as being wonderful sources of noise. I don't much about the design and execution of music servers, but Lukasz Domanski does and his music server is easily among the best (we've tested it against the best from CH, Solution, Linn and Naim and it wipes the floor with them. SOme people are using his servers with £400k+ Tidal Assoluta/Kondo systems and declaring them better than units from Taiko, which cost three times the price!)
Anyway, to summarise, because they sound so much better. It's a bit like asking, why bother anything when a JBL bluetooth speaker can serve just a well.