The robes of a Jedi were never supposed to be a 'uniform' and so it is that this idea is carried forward into these robes. Bearing no insignia of any kind, the robes are meant to merely look as though they are the robes of a traveler. The armour built into the robes is common across the Galaxy - to the point that it's absence would likely raise more questions. Simple, plain and functional in every way a Jedi should strive to dress.
Legal in every system. Though it may become frowned upon in some areas should it become a 'uniform' of the Jedi as opposed to the incognito look it currently has.
To provide traveling Jedi (and others) a light armour option that doesn't immediately announce their allegiance to the Galaxy just from the sight of it alone. On a personal level it is to serve as the armour for my Jedi Knight.