Why should the moon be seen in the first and last day of Ramadan, but in other month like Muharram it is not necessary?

 The difference in the view of the moon is related to all lunar months, but in the Holy month of Ramadan because it is about the necessity or prohibition of fasting and the Eid al-Fitr, Or in the month of Dhi Al-Ahjah (because of the Haj pilgrimage) this issue get a lot  more important and has a lot of general reflection. Hence, Muslims all over the globe are staring at the sky with greater attention so as to know their heavenly duty. So, the importance of this issue is because of the necessity of fasting in the first day of Ramadan and the prohibition of fasting in the Eid al-Fitr, and this issue is not true about other months, for instance, if the day of Ashura is one day later or sooner, no obligation is missed or no permissible action has changed into a forbidden one.