Having children is more of a sacrifice than not having any.
That is one opinion. I would say that the 47,422 women in 2012 who had IVF would disagree with you. Having children is not a sacrifice. Children can enrich your life and make you a better person.
Not having children makes life a lot easier.
In what way ? What happened when I'm old and decrepit ? My kids will look after me and make my life easier.
It is not like the old days where you needed children to plough the fields.
Are you suggesting we bred children for slavery ? I bred mine to make me tea in the morning, clean the house, and provide and extra source of vital income. As well as a council house...
There are some that breed kids for replacement organs. Maybe if we bred humans for replacement parts then the organ donation register would no longer be required.
Humans do, as well as other animals, have sex for pleasure. We are also driven by a biological urge to reproduce. That orgasmic bliss you and your partner feels is natures way of telling you that you done it right and makes you want to do it again.
Birth rates are, in nature, driven by longevity and survivability. Animals and humans are biologically driven to reproduce to help prevent extinction. In the developed world we have kids later in life because we can. Health, wealth, science etc all allow us to reproduce later in life. Reproduction is not a lifestyle choice. It is an essential survival trait for a living species.