If people are suffering because of their Karma, why should we help them? What is the need to be compassionate towards others despite knowing that they are suffering because of their Karma?

It is indeed true that if one undergoes suffering, it is because of the effects of one’s bad karma done in previous births or in the distant past.

But a fact of Karma is that if God’s grace is there, the suffering due to Karma gets reduced.

If someone is doing a good karma, he is going to reap good fruits for it at some time in future.

So, if you are helping someone who is suffering,

1. You may perhaps be the channel through which God’s grace is acting on the person to reduce his suffering.
2. By helping the person genuinely, you are acquiring good karma for you.

My Guru Mata Amritanandamayi (Amma) says that if somebody is suffering is because of their bad karma, extending help can be your dharma! A person fallen into a pit shouts for help.  If a passerby thinks ‘Why should I help? After all, he is suffering his karma’, it is not a right mindset. Instead, he should think, ‘It is my dharma to extend my helping hand to pull the person out of the pit’. That is the right attitude, says Amma.