It's very easy to get absorbed into this world and forget our final destination.
We work, play, laugh, watch tv, entertain ourselves - with no slight thought whatsoever that today or tonight, may be the time, when the angel of death, in charge of us - will carry out his duty, as ordained by Allah SWT.
Sometimes even in doing 'ibadah', (e.g. going for syarahan or giving syarahan, reciting the Quran, advising others etc), we lose our focus or forget the root intentions, and get absorbed in wanting to 'win' the situation or prove something only to ourselves or to others. No longer is the intention for Allah SWT.
So how can we constantly remind ourselves of Allah SWT, of our purpose in life, and our final destination?
I believe that is one of the purpose of our 5 daily prayers. Just like.. why do you think, in schools, we need to say the pledge and sing the national anthem every morning? But Allah knows best - once a day is not enough.
That would also explain why 5 prayers grouped, only to be done at night - will not work. That's besides the fact that we don't even know if it will be accepted by Allah SWT.
We are truly forgetful beings. and Allah knows best, we NEED to be reminded constantly.
With the properly done 5 daily prayers, insyaAllah, we can be in 'constant' reminder. Of course not constant by Rasulullah SAW standards, only constant by our weak standards. Weak as in, even there, right after prayers, while still on the praying mat, I can start to forget. :/
But the efforts and sincere intention counts, I believe.
So we keep on trying.