A. From ancient times special garments were worn by religious leaders. The Torah describes the way the priests were to dress, and indeed one of the most moving features of Yom Kippur in the Temple was the way in which the normal ornate garments of the high priest were replaced by simple white clothing.
In Talmudic times scholars could be recognised by their clothing. Many lands had their own styles of rabbinic garb; see Alfred Rubens’ History of Jewish Costume. Chasidic dress styles are of course well known. So there can be no objection to rabbis and chazanim wearing a type of uniform.
The caps and gowns we are used to were introduced into England by Chief Rabbi Nathan Marcus Adler in the 1840s; the fact that they resemble what is customary in some other faiths is no argument against them provided they have no specifically Christian theological significance.