That puttees are not worn today is partially due to better design of boots, the introduction of motorised transport, the changing nature of warfare and, yes, to military fashion.
For the warfare of the pre-Great War period, puttees were well suited, not so for the Great War in the trenches, where they could not but become waterlogged, contributing to ill health and, of course, they took a degree of training to don them properly (not so with 'Hi=Legs' or gaiters) - and they are a pain to put on properly when wet

Puttees were a practical garment in their time, but their timee is well and truely past (although ankle puttees made a brief comeback in the 1970s in combat dress, only to fade out again).
Tom