Because that's what kindness is. It's not doing something for someone else because they can't, but because you can.

The line distinguishes kindness from pity or condescension. It argues that genuine kindness is not primarily a response to another person’s incapacity (“because they can’t”), which can subtly position the giver as superior. Instead, it frames kindness as a voluntary use of one’s own capacity (“because you can”)—a choice to extend help, attention, or generosity simply because one has the ability and opportunity to do so. The emphasis shifts from judging the recipient’s neediness to recognizing the giver’s responsibility and freedom to act well. In that sense, kindness becomes an ethical posture: using one’s advantages—time, strength, resources, knowledge—to reduce friction for others without making their dependence the defining feature of the interaction.