Well, I didn't set out here to complain about the hard life of a childfree person or to draw any comparisons to the hardships of other groups, really. In general we mostly complain and joke amongst ourselves about first-world problems, though there are sometimes some serious issues which arise. The "demands" are mostly social, in the form of peer pressure, judgement, and discrimination from family, friends, and colleagues. Here are a few examples of "demanding" behaviour and other issues which are discussed often in childfree spaces:

• A parent, sibling, or friend consistently asks a childfree person when they're going to provide them with a grandkid, niece/nephew, etc. Occasionally this crosses the line into serious toxicity and even assault. I recall reading one account of a crazy mother-in-law sneaking into a couple's room and poking holes through their condoms.
• This is actually a pretty alarming one to me: healthcare providers sometimes refuse certain elective procedures (for example vasectomy, tubal ligation) to those who are not "old enough to make that decision." (This happens to adults who are in their 20s and 30s.)
• Believe it or not, there really are people who seem to think people who are childfree by choice are selfish, greedy, or even evil. The author of this post we're commenting under just attacked someone's character for claiming membership in a childfree organisation.
• Constant invalidation of their experiences by parents on the grounds that a childfree person cannot possibly be as exhausted/happy/fulfilled/worried/anguished as they are: "You don't know true love until you have a child. Tired?! You don't know what tired is, until your baby cries all night for an entire week. All of your problems now will seem so small when you eventually decide to have children."
• A childfree individual is often expected to take on an increased workload at their job because they don't have kids so they "must have the time." Those with children tend to get a free pass at their expense.
• In general, society seems to bend over backwards to ensure the safety and welfare of children, no matter what the cost to responsible adults. This can be very annoying, and we like to grumble about it amongst ourselves the way one may complain about the rainy weather or rush-hour traffic.

Again, I didn't set out with the intention of making a big deal about these issues, but I've listed them so you can understand that there is indeed a shared set of experiences among childfree individuals which lends itself to the development of support systems.

To answer your question about benefits: I understand why a society would want to provide soft incentives to bear and raise children. Incentives like tax breaks, benefits, etc. To the extent that I support the existence of a government at all, I do not personally take any serious issue with these things. If you are able to receive financial help for raising your children, I am happy that you and they are well. I don't see that as unfair to me. I see it as an investment in the future of society.