What is the reason for believers to be together all the time?

Allah orders believers in many verses of the Qur’an to be together and not to turn away from believers by desiring the life of this world:

Hold fast to the rope of Allah all together, and do not separate. Remember Allah’s blessing to you when you were enemies and He joined your hearts together so that you became brothers by His blessing. You were on the very brink of the pit of the Fire and He rescued you from it. In this way Allah makes His Signs clear to you, so that hopefully you will be guided. (Surat Al Imran, 103)

A person who lives according to the Qur’an is surely bound to obey these commands of Allah like all of Allah’s other commands. To be with the believers is a great blessing and a support for every human being. For instance, after Allah gave Musa (as) the responsibility of prophethood, Musa (as) asked for his brother Harun (as) to be a helper to him. Believers always remind each other about Allah, they forbid one another to commit evil acts or make mistakes, they help each other and cooperate in every way possible. Also, of all people, believers are the ones who have the highest moral standards and who always act conscientiously. Therefore, the most peaceful environments are those in which the believers live together.

What is the reason for believers to be together all the time?