ParisMaman, If you are asking why American/Western society pushes learning on such young children, then now I understand your question/concern. If not, then just skip over the rest of this post.
As you already know, it is true that mainstream American society puts a lot of pressure on children to grow up quickly. We are a very competitive society and, IMHO, that often is horrible for the child and for the well-being of our culture. Among many other things, trying to make one's baby "smarter" than other babies by teaching them the elementary basics (reading, writing, math) before they even start kindergarten is popular among many families. I have heard many MANY mothers brag over how their child can already read (when the child is only 2 or 3), etc. There are always articles in the mainstreamed parenting magazines (not Mothering of course) on how to give your toddler/baby a headstart in learning. There are many baby toys that encourage early learning of ABC's, phonics and math. There are monthly book clubs for babies. There are even subscriptions for learning packets (which consists of a workbook, craft, storybook, and learning game) to be sent to your home once a month for children starting as young as 2 yrs old. Making your child "smarter" is like one big race and many parents buy into it.
I was one of those mothers when my daughter was born. I bought into a lot of the learning toys, and I even bought the monthly workbook. My daughter wanted nothing to do with all that stuff, it was a battle just to get her to look at them. She would rather play with the fern fluff in our yard (she would pretend they were fairies flying in the breeze), or go on "animal adventures" outside, or play pretend, among many other naturally fun ways of learning. She would play with her toys and look at books, but only when she wanted to, never if she was pushed. SHE taught ME what was right for her. I learned my lesson. Society is wrong to push learning on children, especially with of all of these artificial tools to do so. If the child shows a genuine interest in those tools, then great, but it shouldn't be pushed on a child of any age, especially a baby/toddler.
That said, my daughter now attends elementary school (1st grade) where she is required to do homework daily, she is required to read a certain number of books each day/week, she is expected to do all of the classwork the teacher gives her, she is pressured and bribed to behave nicely (2 students are rewarded as "good citizen" each month). Is this natural child-led learning? Should there really be a cut-off age (currently 4 to 5 yrs) where the child starts learning by force? Hmmmm......maybe that's why "learning" no longer becomes fun when we get older. It's a double-edged sword, though, because in order to function in this society one has to get used to doing things they don't always want to do (school/work) and we have to conform to a certain degree in order to succeed. The more one conforms, the better they succeed. I guess schooling conditions the child (starting as young as 2) for competitive American life. Is that a good thing? Maybe...maybe not.
It is much easier to see a need for change than it is to actually make the change (in this case anyway).
Whew...that was intense.