one use or not, drones experience vibration which can cause a cable to come loose and loss of the aircraft. cable management helps ensure that all the cables keep all the cables seated, among other things
I don't know what it's "for" but the point of Ukrainian drone technology is to be cheap and plentiful, so it makes a lot of since. An amateur would try to design their own bespoke system that fills their goals perfectly, but in reality they can't manufacture in any sufficient quantities.
All those FPV drones that they are using are not pretty. It's the absolute bare-bones drone that they can get. Their effectiveness has been shown over and over again in videos. It's not about aesthetics, it's about effectiveness.