The same logic dictates that all signs in the country should be in English because everyone learns English from a young age so they don't need Hebrew or Arabic. A government's job is to make sure all its citizens are represented and taken into consideration. Arabic (and even Russian) signs are obviously required because those are the demographics of Israel.
Donald Trump: Israeli settlement construction in West Bank should 'keep going' (Haaretz)
from the article: Supreme Court supports Arabic, but court museum shuns it