There are no logical reasons to have children. If we were all Vulcans, we would not reproduce and therefore die out fairly quickly. (Actually, I wonder WHY Vulcans have kids.) Not only are there no logical reasons for having kids, they also come with quite the expensive price tag. The (fully consensual) decision to reproduce is entirely emotional.
Having children is a tremendously expensive emotional luxury (and/or obligation, depending on the level of reproductive consent). If fertility control were perfect and widespread, kids would be nothing but a luxury. But because reproduction also comes with a biological imperative and our fertility control is not perfect due to flaws in access, education, and the technologies themselves, the luxury and cost of children is not something accorded only to those who explicitly consent to reproduce. One could argue that there is an implicit reproductive consent that comes with (consensual) heterosexual coitus, but given the number of after-the-fact fertility control technologies and the number of people who use them, it is clear that many dispute the validity of that implicit consent by their very choices.
Given this murky context of implicit and explicit (or coercive) reproductive consent, it is really no surprise that the moralists have colonized this issue. The idea then becomes that there is a MORAL reason why consent can often become irrelevant to whether any given person reproduces. Various religious dogmas support and encourage the production of more Christian or Jewish soldiers to populate the world. Many of those same dogmas also condemn the single and/or teenage mother for her pregnancy, couching it as the price of her slut-itude (the attitude and lifestyle of being a slut, in case you were wondering). Children then become both the goal of the morally righteous and the price of the morally bankrupt.
Of course, these musings only really apply to modern developed society. Before widely effective fertility control methods became available, there was a much closer coupling of the consent/coercion of heterosexual coitus to the consent/coercion of reproduction. Also, in agricultural and early industrial revolution society, children were of economic benefit to their families. They could work on the farm or earn wages at child labor (albeit in often horrific working conditions). (There is quite the possibility that kids were also an asset in pre-agricultural society, but I don't know as much about it.)
I do not condone nor advocate a repeal of child labor laws by any means, but it is worth pointing out that our current economic system is set up so that a child is nothing but a drain on their parents' resources until they become working age and begin paying their own way. Not only does it cost resources for clothing, food, housing, etc., but there are other costs as well. There are the childcare costs, the time and labor of potty training, and the general incompatibility of the corporate workplace (with some notable exceptions) to the demands of parenthood.
Furthermore, women carry the majority of the burden for childbearing. Not only is there is biological cost of gestation and labor (and possibly lactation), but there is also the added economic cost of missed work, a glass ceiling effect due to being shunted onto the "mommy track," and the "second shift" burden of being expected to shoulder the majority of the caretaking and housekeeping regardless of other breadwinning accomplishments.
Perhaps it is this very lack of economic viability of reproduction that will be our salvation as a species on this planet. Perhaps as the global levels of education for women and overall access to reproductive planning services and technology increase, and more of the world moves to a "developed" economy, the luxury of kids will become less and less of a viable choice and worldwide fertility rates will continue to fall until we move into negative population growth. Perhaps lessening our ecological footprint via negative population growth will be what keeps humans from destroying our global habitat.
Or perhaps we just need to realize our gross sexism and institutional hostility toward parents and fix it.