Why should we cherish others? Why should we take the Bodhisattva vow and perform the various Bodhisattva practices to benefit other beings? What have others ever done for me?!
(a) Because they are beings just like you. They experience happiness and suffering in the same way as you. They want happiness and want to avoid suffering as you do. They deserve to be happy as you do. They have the same capacity to develop positive qualities such as loving kindness, universal compassion, bodhicitta, and a realization of emptiness as you do. They have the same capacity to become a buddha as you do. But unlike you they are many and you are one.
(b) Because strangers have helped you. In your home you might have electricity, internet access, clean water coming in, sewerage going out, post brought to your door, and rubbish taken away. In your town you have streets, a car, buses, trains, aeroplanes, supermarkets and other shops to provide everything from the shirt on your back to the food in your belly. In your life, the language that you speak and read, the education that you have, the job where you work. None of these are made by you, they all depend on a vast network of kind beings that you will never meet. If you accept reincarnation, then others have also helped you in innumerable past lives.
(c) Because friends and family have shown you kindness. Let’s start with the woman that gave birth to you and whoever got you through those fragile 3-5 years when you could have easily died without the right food, water, clean clothing and bedding, heating, coolness, somebody speaking to you to prompt you to speak, showing you affection to prompt you to develop kindness, and other necessities. Every relative, friend, work colleague, and those people you know well enough to give a head-nod. Again, there are all of these people being kind to you, and unlike you they are many and you are one. Again, if you accept reincarnation, then others have shown you this same type of kindness in innumerable past lives.