There is nothing inherent in life that causes it to 'need' to exist. The only premise that leads most people to believe otherwise, unfortunately, is stupidly simple: they are alive. Having grown emotionally attached to an ego that comprises all of their triumphs and struggles, they feel threatened when someone challenges their preconception that life is sacred. This is quite problematic, and needs to be addressed if we are to actually fix the world in which we live.
Inevitably, many who are presented the possibility that life has no purpose, or the possibility that it is the direct cause of everything negative that has ever existed, will become defensive. No one wants to hear that they aren't accomplishing anything by existing, after all, or that the universe would be better off without them while in a state of absolute zero value. Submission to the various genetically and memetically motivated drives which cause a person to do whatever pleases him or her, or whatever gives him or her a sense of entitlement, is difficult to break, even in spite of the resource cost that such irresponsible behavior generates.
Yet, despite the general population's repugnantly selfish repudiation of the harsher aspects of reality, you'll hardly find anyone who lacks empathy for the dying, the sick, the handicapped, or anyone else who may experience intense suffering. Why is this? Is it really because we generate a positive when we save a life or nurse a sickly person back to health?
The answer to this question, ultimately, is no. Doing anything for a suffering person that might ease his or her pain merely terminates a negative; it does NOT produce a real positive. In any case, when most people display empathy* for their fellow man, it's in a grotesquely narrow fashion, and only pertains to those suffering within close proximity. Subjective preferences and other forms of cognitive bias distort the average person's perception to the point where suffering is "just the way the world works," yet when this same phenomenon comes knocking on their own doors, so to speak, it's suddenly the end of the world. Over two hundred thousand people die every day, but no one bats an eye, because that's part of the "circle of life." When it's time to attend a loved one's funeral, however, it's suddenly acceptable to break out the tissues.
Crying over the death of anyone, of course, will not bring them back, nor will it undo the traumatizing experiences that led to their demise. Having emotional preferences for living organisms, therefore, while mostly unavoidable at the moment, is plainly dangerous; it retards productivity, and ignores the vast majority of all life that has ever mattered in favor of some emotional preoccupation -- a symptom of a problem that itself can lead to racial segregation and genocide, just to name two of its uglier manifestations. You can like chocolate ice cream more than vanilla ice cream on a purely subjective level, but if chocolate ice cream feels pain when you chomp into it, the logical choice is the vanilla ice cream. And if the prevailing trend is to fail to adhere to this most basic of principles? Remain indefinitely alarmed in the general sense rather than occasionally and in singular instances -- no crying required.
No one gets diabetes checkups for their children in order to be a "good" person, or in order to make the world a better place, or in order to be productive. They do it because it makes them feel good -- much like any form of emotional altruism does -- to have something to accomplish in life. If their children were to not exist, then there'd be no diabetes to treat. Of course, there'd also be no mission to embark upon, and the mission is all that matters to anyone.
Anything which justifies a person's own existence and fortifies his or her DNA-obeying ego is what wins out in the end. Never mind that no one consents to being born and that society merely pretends to value consent; people are necessary, and deserve medals every time they clean up fifty percent of a spill that they purposely engineered in the first place. In short, the petty ego satisfaction of those who have children overrides all of the runny noses and car accidents that they wind up causing along the way.
* Empathy in any form is a bias; it has nothing to do with defining qualities or values, but rather with psychological satisfaction, which is irrelevant to pragmatic work, and often illogical or selfish. All that matters is that we assess a given situation based on past experience and a workable values system, then come to a tentative conclusion and act. You don't need empathy for specific living things in order to agree that something needs to be done about life as a whole.