Passing on Al Sirat Al Mostakim (the straight path) is very difficult because the partners of this path, even if they’re from the greatest people, are few; passing through this path should be despite the lack of companionship. That’s why the Prince of Believers (pbuh), who was himself a straight path, says: "Do not find the path of truth desolate due to the paucity of its followers".  Therefore, Al Sirat Al Mostakim is not full of followers, that’s why passing through it needs relentless pursuit and a long time in order for a human being to reach the rank of the pious and be one of God’s people.
Another reason for the lack of companionship in Al Sirat is that despite God mentioned (those who are bestowed by God’s favor), (those who have evoked God’s anger), and (those who are astray) in the plural form, in the Holy Qur’an, in the verse that still under study, the prince of believers (pbuh) categorized people into 3 types in his Hadith by pluralizing only one kind of them by saying: "There are 3 types of people: a divine scholar, a seeker of knowledge for the sake of deliverance, and disreputable people who follow every caller and bend in the direction of every wind" (which means they follow whoever calls for them).
Another evidence for the lack of companionship in the trip of Al Sirat Al Mostaim is that God almighty says about hell:( I will surely fill the hell with Jinn and people all together) but he didn’t say that he will fill heaven because those who will fill hell are a lot but those who will enter heaven are few.
Accordingly, the path of right is desolate and full of difficulties because of the lack of companionship. Therefore, the Prince of Believers recommends not to feel desolate because of the insignificant number of people who cross the straight path since despite their small number, they are all from pious people.
Ayatollah Sheikh Javadi Amoli
 Nahj Al Balagha, the lecture 201, part 1.
 Same source, proverb no 147
 Surat Al Sajdah, the verse 13