Islam is a complete way of life that organizes and arranges every aspect of man’s life. It means that Islam is a comprehensive religion that lays down rules and regulations that set all affairs of man whether secular or religious.
By this meaning, a politician, economist, scientist, etc. should resort to Islam in their behaviour and works. A politician should not support laws that violate the Islamic Shari`ah; an economist should not deal with Riba, etc. Apparently, no single person is asked to do or know all professions.
Islam as a religion that deals with all aspects of life organizes man’s life in the best way and highest order. Therefore, if you follow the Islamic guidance in all aspects of life, this will bring you more fruits which may not be clear to some people. For example, if you reflect on the Prophet instructions to eat with the right hand and to use the left hand in cleaning the private parts after answering the call of nature, it may indicate that by doing so your food is protected from invisible traces of contamination.
Also, in Islam there are ta`abbudi issues whose wisdom and aim may not grasped by people and the Muslim does them to seek Allah’s pleasure and reward. This includes the matters you have mentioned which are not obligatory to be followed. However, if a Muslim has done them, he will be rewarded by Allah and if he did not do them, he will not be punished.