Then Allah tells:

قُلْ أَرَأَيْتُمْ إِن جَعَلَ اللَّهُ عَلَيْكُمُ النَّهَارَ سَرْمَدًا إِلَى يَوْمِ الْقِيَامَةِ ...

Say: "Tell me! If Allah made the day continuous for you till the Day of Resurrection,

Allah tells us that if He had made the day continuous, lasting until the Day of Resurrection, that would also be harmful for them and their bodies would get tired from so much movement and activity.

Allah says:

... مَنْ إِلَهٌ غَيْرُ اللَّهِ يَأْتِيكُم بِلَيْلٍ تَسْكُنُونَ فِيهِ ...

which god besides Allah could bring you night wherein you rest!

meaning, `to rest from your work and activity.'

... أَفَلَا تُبْصِرُونَ ﴿٧٢﴾

وَمِن رَّحْمَتِهِ ...

Will you not then see, It is out of His mercy, (towards you),

... جَعَلَ لَكُمُ اللَّيْلَ وَالنَّهَارَ ...

that He has made for you the night and the day,

i.e. He created both,

... لِتَسْكُنُوا فِيهِ ...

that you may rest therein, (during the night),

... وَلِتَبْتَغُوا مِن فَضْلِهِ ...

and that you may seek of His bounty,

during the day, by traveling, moving about and working.

... وَلَعَلَّكُمْ تَشْكُرُونَ ﴿٧٣﴾

and in order that you may be grateful.

So that you may give thanks to Allah by performing all kinds of acts of worship at night and during the day. Whoever misses something during the night can make it up during the day, and vice versa.

This is like the Ayah,

وَهُوَ الَّذِى جَعَلَ الَّيْلَ وَالنَّهَارَ خِلْفَةً لِّمَنْ أَرَادَ أَن يَذَّكَّرَ أَوْ أَرَادَ شُكُوراً

And He it is Who has put the night and the day in succession, for such who desires to remember or desires to show his gratitude. (25:62)

And there are many similar Ayat.