'Then find another religion'. In Israel that often still means you cannot get married. Judaism might be a state religion as Sherlock also says, but in many countries the state religion is no impedement for people of different backgrounds to marry in civil fashion, including the country where I grew up which is protestant but allows interfaith and gay marriage. Back to Israel: do not underestimate the difficulties of millions of immigrants to the country in this respect - what choice do they have? Lastly, established customs??? Judaism is more than some would like it to be. This goes for all religions. If we followed all the laws our society would grind to a halt and modernity would be swept away.
Palestinian man suffers light wounds from rocks thrown by Jewish men in Jerusalem (Haaretz)
from the article: Police arrest Women of the Wall leader for praying with Torah scroll