First, it can absorb energy at night and store it.
The physical protection it offers might not be much used since Gauss masters protective magic in most cases, but an extra layer of strong protection is always better.
No adventurer has ever complained about having too many means of defense; the robe restricts a professional's actions far less than armor does.
Moreover, it can provide specific soul and mental defense, further expanding Gauss's dimensions of protection.
In fact, the higher the power level, the greater the probability of involving the mental dimension.
The third effect is that Gauss need not worry about its repair if damaged, and the self-cleaning feature is quite good, always maintaining elegance and cleanliness.
