Praise be to Allah.
You have to realize that the question you have asked is very dangerous, because it could be applied to all the rulings of sharee’ah. A person could ask, we do we have to fast a whole month all at once (Ramadaan), why aren’t the days spread out throughout the year? Why is Hajj with its rituals done only at one particular time of the year, when people have to be all crowded together; why can’t it be done at other times of the year too? There are many questions which may imply that one is objecting to the rulings of Allaah. Do you know that Allaah says (interpretation of the meaning):
“Verily, As Salaah (the prayer) is enjoined on the believers at fixed hours” [al-Nisaa’ 4:103]?
i.e., it is obligatory at those times. So understand what has been said above, and I ask Allaah to guide you and set your heart straight.
Shaykh Sa’d al-Humayd
Islam means submitting to Allaah and not objecting to His commands. Allaah says (interpretation of the meaning):
“It is not for a believer, man or woman, when Allaah and His Messenger have decreed a matter that they should have any option in their decision” [al-Ahzaab 33:36]
And Allaah says concerning the timings of the prayer:
“Verily, As Salaah (the prayer) is enjoined on the believers at fixed hours” [al-Nisaa’ 4:103]
The wahy (revelation, i.e., Qur’aan and Sunnah) described the times of prayer in both word and deed. This is how the Prophet (peace and blessings of Allaah be upon him) did the prayers during his lifetime; he did not join prayers together except when he was travelling or at times of hardship.
We also want to advise you that there are some followers of bid’ah (reprehensible innovation) who say that Zuhr and ‘Asr should be joined together, as should Maghrib and ‘Ishaa’, even when one is not travelling and for no reason. Beware of these people, do not keep company with them and do not listen to them. Beware of them lest they lead you astray from your religion. We ask Allaah to grant you strength and guidance.