Don't get it twisted walaal, it is not unique to Somalis. All insular ethnic groups that are culturally homogenous and conservative generally expect you to adhere certain social norms.
Even liberal ethnic groups like some Scandinavians have societal expectations which pressure people to conform to the dominant cultural customs.
You are also forgetting that we are relative newcomers to the West and are still going through the process of assimilation. Change, not necessarily good, is already happening. Give it another few decades and Somali social taboos will cease to exist among the assimilated majority.