It would be illegal in the UK to drive without windscreen wipers - however headlight washer systems are not compulsory although for SVA purposes you would not pass if you have HID lamps and no washer.
The reason, as far as I understand it, is that HID systems generate more heat than a collapsing star and that water evaporating on the glass will leave a residue obscuring the lamp, which will, in turn, overheat and fail.
I hope this has been illuminating.
Jingle Bells.
