Over 1/5 of Israel’s population is Arab. Why not accommodate them by providing signage in Arabic? BTW, enabling 1/5 of a country’s citizens to understand signage (be it directions, instruction, earning, etc…) also helps the non-Arabic speaking population. Also, I’ve only seen Arabic signage in certain cities which have a large Arab population, probably much higher than 1/5 (ie: in Jerusalem, but nor in Tzfat).
And what’s the harm in such signage? Why does it upset you?